Pass-through implantable medical device delivery catheter with removeable distal tip

ABSTRACT

In one example, this disclosure is directed to a kit for intravascular implantation of an implantable medical device, the kit comprising an outer sheath, the outer sheath sized to traverse a vasculature of the patient, and an elongated inner sheath with a tapered distal end. The inner sheath is slidable within the inner lumen of the outer sheath and is selectably removable from the inner lumen of the outer sheath by sliding the inner sheath out of the proximal opening of the outer sheath. The kit includes an elongated deployment receptacle including a deployment bay slidable within the inner lumen of the outer sheath when the inner sheath is not within the inner lumen of the outer sheath. The deployment bay carries an implantable medical device through the inner lumen of the outer sheath and facilitates deployment of the implantable medical device from the distal end of the outer sheath.

This application claims the benefit of U.S. Provisional PatentApplication No. 61/615,715, filed Mar. 26, 2012, the entire content ofwhich is incorporated by reference herein.

TECHNICAL FIELD

This disclosure relates to delivery and deployment techniques forimplantable medical devices.

BACKGROUND

Various implantable medical devices (IMDs) may be used fortherapeutically treating or monitoring one or more physiologicalconditions of a patient. Such IMDs may be adapted to monitor or treatconditions or functions relating to heart, blood vessels, muscle, nerve,brain, stomach, endocrine organs or other organs and their relatedfunctions. Advances in design and manufacture of miniaturized IMDs haveresulted in IMDs capable of therapeutic as well as diagnostic functionssuch as pacemakers, cardioverters, defibrillators, biochemical sensors,pressure sensors, various endovascular IMDs and the like. Such IMDs mayhave electronic functions and may be associated with electrical leads ormay be wireless, with the ability to transmit data electronically eitherto another IMD implanted in the patient or to another device locatedexternally of the patient, or both. Other IMDs may have purelymechanical and/or pharmaceutical functions, such as stents.

Although implantation of some IMDs requires a surgical procedure (e.g.,pacemakers, defibrillators, etc.) other IMDs may be small enough to bedelivered and placed at an intended deployment site in a relativelynoninvasive manner, such as by a delivery catheter introducedpercutaneously. Delivery also may be accomplished by advancing acatheter intravascularly through an exposed vasculature during asurgical procedure.

SUMMARY

In different examples, this disclosure describes techniques for remotedeployment of IMDs.

In one example, this disclosure is directed to a kit for intravascularimplantation of an implantable medical device within a patient, the kitcomprising an elongated inner sheath with a distal end, a first couplingmodule slidably connected to the inner sheath, an elongated outer sheathforming an inner lumen with a distal opening and a proximal opening, theouter sheath sized to traverse a vasculature of the patient. Theproximal opening is configured to receive the distal end of the innersheath. The inner lumen is sized to receive the inner sheath and tocontain the implantable medical device. The kit further comprises amating coupling module secured to a proximal end of the outer sheath.The mating coupling module is configured to connect to the firstcoupling module such that the inner sheath is axially aligned with theouter sheath. The inner sheath is slidable within the outer sheath whilethe first coupling module is connected to the mating coupling module.

In another example, this disclosure is directed to a method forintravascular implantation of an implantable medical device within apatient comprising positioning a distal end of an elongated outer sheathvia a vasculature of the patient proximate to a target site within thepatient. The outer sheath forms an inner lumen with a distal opening anda proximal opening. The method further includes connecting a firstcoupling module that is slidably connected to an elongated inner sheathwith a mating coupling module secured to a proximal end of the outersheath. The mating coupling module is configured to connect to the firstcoupling module such that the inner sheath is axially aligned with theouter sheath. The inner sheath has a distal end. An implantable medicaldevice is positioned in the inner lumen of the outer sheath. The methodfurther includes pushing the implantable medical device through theinner lumen of the outer sheath and out of the distal opening with theinner sheath to deploy the implantable medical device proximate to thetarget site within the patient.

In a different example, this disclosure is directed to a kit forintravascular implantation of an implantable medical device within apatient, the kit comprising an elongated outer sheath forming an innerlumen with a distal opening and a proximal opening, the outer sheathsized to traverse a vasculature of the patient. The kit further includesan elongated inner sheath with a tapered distal end. The tapered distalend is configured to substantially fill the inner lumen of the outersheath and close-off the distal opening of the outer sheath. The innersheath is slidable within the inner lumen of the outer sheath. The innersheath is selectably removable from the inner lumen of the outer sheathby sliding the inner sheath out of the proximal opening of the outersheath. The kit further includes an elongated deployment receptacleincluding a deployment bay at a distal end of the deployment receptacle.The deployment receptacle is slidable within the inner lumen of theouter sheath when the inner sheath is not within the inner lumen of theouter sheath. The deployment bay is configured to carry an implantablemedical device through the inner lumen of the outer sheath andfacilitate deployment of the implantable medical device out of thedistal opening of the outer sheath.

In another example, this disclosure is directed to a method forintravascular implantation of an implantable medical device within apatient comprising positioning a distal end of an elongated outer sheathvia a vasculature of the patient proximate to a target site within thepatient. The outer sheath forms an inner lumen with a distal opening anda proximal opening. The method further includes inserting an elongateddeployment receptacle including a deployment bay at a distal end of thedeployment receptacle into the proximal opening of the outer sheath. Animplantable medical device is positioned within deployment bay, slidingthe deployment receptacle through the inner lumen of the outer sheathuntil the deployment bay is adjacent to the distal opening of the outersheath, and deploying the implantable medical device from the deploymentbay proximate to the target site within the patient.

In a different example, this disclosure is directed to a kit forintravascular implantation of an implantable medical device within apatient, the kit comprising an elongated outer sheath forming an innerlumen with a distal opening, the outer sheath sized to traverse avasculature of the patient. The kit further includes an elongated innersheath with an inflatable member at a distal portion of the innersheath. The inflatable member is selectively inflatable from a proximalend of the inner sheath. The inflatable member is configured tosubstantially fill the inner lumen and close-off the distal opening ofthe outer sheath when inflated. The inner sheath is slidable within theinner lumen of the outer sheath. The inner sheath further includes astopper proximally located relative to the inflatable member. Theinflatable member is remotely controllable from a proximal end of theinner sheath to retract in a proximal direction towards the stopper. Thekit is configured such that the inflatable member can be retracted in aproximal direction towards the stopper and past an implantable medicaldevice positioned within a distal portion of the outer sheath.

In another example, this disclosure is directed to a method forintravascular implantation of an implantable medical device within apatient comprising positioning a distal end of an assembly including anelongated outer sheath and an elongated inner sheath via a vasculatureof the patient proximate to a target site within the patient. The outersheath forms an inner lumen with a distal opening. The inner sheathincludes an inflatable member at a distal portion of the inner sheath.The inflatable member is selectively inflatable from a proximal end ofthe inner sheath. The inflatable member is inflated to substantiallyfill the inner lumen and close-off the distal opening of the outersheath. The inner sheath further includes a stopper proximally locatedrelative to the inflatable member. The inner sheath is slidable withinthe inner lumen of the outer sheath. The method further includesdeflating the inflatable member, and retracting the inflatable member ina proximal direction towards the stopper and past an implantable medicaldevice that is positioned within a distal portion of the outer sheath.

In a different example, this disclosure is directed to a kit forintravascular implantation of an implantable medical device within apatient, the kit comprising an elongated outer sheath forming an innerlumen with a distal opening, the outer sheath sized to traverse avasculature of the patient. The kit further includes an elongated innersheath with an enlarged distal portion. The enlarged distal portion isconfigured to substantially fill the inner lumen and close-off thedistal opening of the outer sheath. The enlarged distal portion isslidable relative to the outer sheath. The inner sheath further includesa tether with a helical element that is remotely controllable from aproximal end of the inner sheath to release the implantable medicaldevice from a distal portion of the outer sheath.

In another example, this disclosure is directed to a method forintravascular implantation of an implantable medical device within apatient comprising positioning a distal end of an assembly including anelongated outer sheath and an elongated inner sheath via a vasculatureof the patient proximate to a target site within the patient. The outersheath forms an inner lumen with a distal opening. The inner sheathincludes enlarged distal portion. The enlarged distal portionsubstantially fills the inner lumen to close-off the distal opening ofthe outer sheath. The enlarged distal portion is slidable relative tothe outer sheath. The inner sheath further includes a tether with ahelical element. The method further includes releasing an implantablemedical device from a distal portion of the outer sheath by remotelyrotating the helical element such that the helical element releases alooped element of the implantable medical device.

In a different example, this disclosure is directed to a kit forintravascular implantation of an implantable medical device within apatient, the kit comprising an elongated outer sheath forming a firstinner lumen with a distal opening, the outer sheath sized to traverse avasculature of the patient. The kit further includes an elongated innersheath forming a second inner lumen. An outer diameter of the innersheath is smaller than the diameter of the first inner lumen such thatthe inner sheath fits within the first inner lumen. The inner sheath isslidable within the first inner lumen. The second inner lumen at adistal end of the inner sheath is configured to carry an implantablemedical device. The inner sheath forms a slit at a distal end of theinner sheath to facilitate deployment of the implantable medical deviceout of the distal opening of the outer sheath.

In another example, this disclosure is directed to a method forintravascular implantation of an implantable medical device within apatient comprising positioning a distal end of an assembly including anelongated outer sheath and an elongated inner sheath via a vasculatureof the patient proximate to a target site within the patient. The outersheath forms an inner lumen with a distal opening. The inner sheathforms a second inner lumen. An outer diameter of the inner sheath issmaller than the diameter of the first inner lumen such that the innersheath fits within the first inner lumen. The inner sheath is slidablewithin the first inner lumen. Assembly further includes an implantablemedical device carried within the second inner lumen at a distal end ofthe inner sheath. The inner sheath forms a slit at a distal end of theinner sheath to facilitate deployment of the implantable medical deviceout of the distal opening of the outer sheath. The method furtherincludes sliding the distal end of the inner sheath out of the firstinner lumen to expose a portion of the inner sheath and a portion of theimplantable medical device out of the distal end of the outer sheath.

In a different example, this disclosure is directed to a method forintravascular implantation of an implantable medical device within apatient comprising positioning a distal end of an elongated outer sheathforming an inner lumen with a distal opening adjacent a target sitewithin a vasculature of a patient, partially deploying an implantablemedical device from the distal opening. The implantable medical deviceincludes an expandable fixation element expandable from a collapsedposition to an expanded position, wherein at least a portion of theexpandable fixation element assumes the expanded position when theimplantable medical device is partially deployed from the distalopening. The method further comprises advancing the distal end of theouter sheath within the vasculature with the implantable medical devicepartially deployed from the distal opening, monitoring at least one ofthe vasculature and the portion of the expandable fixation element fordeflection to determine when the size of the portion of the expandablefixation element corresponds to the size of the vasculature.

In a different example, this disclosure is directed to a kit forintravascular implantation of an implantable medical device within apatient, the kit comprising an elongated outer sheath forming an innerlumen with a distal opening, the outer sheath sized to traverse avasculature of the patient. The kit further includes an elongated innersheath with a stopper configured engage a proximal side of theimplantable medical device to preclude the implantable medical devicefrom being located at a more proximal position than the stopper withinthe inner lumen of the outer sheath. The inner sheath further includes atether configured to form a loop on a distal side of the stopper, theloop being configured to engage a looped element of the implantablemedical device to couple the implantable medical device to the innersheath. The stopper is slidable relative to the outer sheath between aposition that is proximally located relative to the distal opening ofthe outer sheath and a position in which at least a portion of thestopper is distally located relative to the distal opening of the outersheath. The tether is configured to release the looped element of theimplantable medical device from the inner sheath by opening the tetherloop when the at least a portion of the stopper is located distallyrelative to the distal opening of the outer sheath.

In another example, this disclosure is directed to a kit forintravascular implantation of an implantable medical device within apatient, the kit comprising an elongated outer sheath forming an innerlumen with a distal opening. The outer sheath sized to traverse avasculature of the patient. The inner lumen is sized to hold theimplantable medical device. The kit further includes an elongated innersheath with a distal end. The inner sheath is located within the innerlumen of the outer sheath, and a deployment handle located at proximalends of the outer sheath and the inner sheath. The deployment handleincludes a sheath retraction mechanism that facilitates selectivelyretracting the outer sheath relative to the inner sheath to facilitateremote deployment of the implantable medical device out of the distalopening of the inner lumen of the outer sheath.

In another example, this disclosure is directed to a method forintravascular implantation of an implantable medical device within apatient comprising positioning a distal end of an assembly including anelongated outer sheath and an elongated inner sheath via a vasculatureof the patient proximate to a target site within the patient. The outersheath forms an inner lumen with a distal opening. The inner sheathincludes a stopper configured to engage a proximal side of theimplantable medical device to preclude the implantable medical devicefrom being located at a more proximal position than the stopper withinthe inner lumen of the outer sheath. The inner sheath further includes atether forming a loop on a distal side of the stopper, the loop being inengagement with a looped element of the implantable medical device tocouple the implantable medical device to the inner sheath within theinner lumen of the outer sheath. The method further comprises retractingthe outer sheath relative to the inner sheath such that the implantablemedical device exits the inner lumen via the distal opening.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a conceptual drawing illustrating an example system thatincludes an implantable medical device (IMD) coupled to implantablemedical leads and a leadless sensor.

FIG. 2 is a conceptual drawing illustrating, in greater detail, theexample IMD, leads, and sensor of FIG. 1 in conjunction with a heart.

FIG. 3 is a conceptual diagram illustrating an example therapy systemcomprising a leadless IMD that may be used to monitor one or morephysiological parameters of a patient and/or provide therapy to theheart of a patient.

FIG. 4 illustrates the leadless IMD of FIG. 3 in further detail.

FIG. 5 illustrates a leadless IMD including an expandable fixationelement configured for securing the leadless IMD within a vasculature.

FIGS. 6-8E illustrate an example system for intravascular delivery of anIMD during an implantation procedure.

FIGS. 9A-9D illustrate example techniques for intravascular delivery ofa sheath.

FIGS. 10A-10D illustrate example techniques for intravascular deliveryof an IMD through a sheath using a deployment receptacle.

FIGS. 11A-11D illustrate example techniques for intravascular deliveryof an outer sheath using an inner sheath with a distal inflatablemember.

FIGS. 12A-12C illustrate example techniques for intravascular deliveryof an IMD using a delivery catheter with a distal inflatable member.

FIGS. 13A-13B illustrate the distal end of an inner sheath with aninflatable member as shown in FIGS. 12A-12C in further detail.

FIG. 14 illustrates the distal end of an inner sheath with an inflatablemember and a distal tapered flexible tip.

FIGS. 15A-15F illustrate example techniques for intravascular deliveryof an IMD using a delivery catheter with a slidable inner sheathincluding an enlarged distal portion and a tether.

FIGS. 16A-16B illustrate example techniques for intravascular deliveryof an IMD using a delivery catheter with a slidable inner sheathincluding an inflatable distal portion and a tether.

FIGS. 17A-17E illustrate example techniques for intravascular deliveryof an IMD using an inner sheath being configured to carry an IMD at itsdistal end, the inner sheath forming a slit at its distal end tofacilitate deployment of the IMD.

FIGS. 18-8C illustrate example techniques for measuring the size of avasculature using a partially deployed IMD within the deploymentreceptacle of FIGS. 10A-10D.

FIG. 19 illustrates example techniques for measuring the size of avasculature using a partially deployed IMD within the inner sheath ofFIGS. 17-7E.

FIG. 20 illustrates example techniques for measuring the size of avasculature using the delivery catheter with an inner sheath includingan inflatable distal portion of FIGS. 16A-16B.

FIG. 21 is a flowchart illustrating example techniques for measuring thesize of a vasculature using a partially deployed IMD.

FIGS. 22-24C illustrate example techniques for intravascular delivery ofan IMD using a delivery catheter that includes a tether forming a loopto engage a looped element of the IMD.

DETAILED DESCRIPTION

FIG. 1 is a conceptual diagram illustrating an example medical system 10that may be used for sensing of physiological parameters of patient 14and/or to provide therapy to heart 12 of patient 14. Medical system 10includes an IMD 16, which is coupled to leads 18, 20, and 22, andprogrammer 24. IMD 16 may be, for example, an implantable pacemaker,cardioverter, and/or defibrillator that provides electrical signals toheart 12 via electrodes coupled to one or more of leads 18, 20, and 22.Patient 14 is ordinarily, but not necessarily, a human patient.

IMD 16 may include electronics and other internal components necessaryor desirable for executing the functions associated with the device. Inone example, IMD 16 includes one or more processors, memory, a signalgenerator, sensing module and telemetry modules, and a power source. Ingeneral, memory of IMD 16 may include computer-readable instructionsthat, when executed by a processor of the IMD, cause it to performvarious functions attributed to the device herein. For example, aprocessor of IMD 16 may control the signal generator and sensing moduleaccording to instructions and/or data stored on memory to delivertherapy to patient 14 and perform other functions related to treatingcondition(s) of the patient with IMD 16.

The signal generator of IMD 16 may generate electrical stimulation thatis delivered to patient 12 via electrode(s) on one or more of leads 18,20, and 22, in order to provide, e.g., cardiac sensing, pacing signals,or cardioversion/defibrillation shocks.

The sensing module of IMD 16 may monitor electrical signals fromelectrode(s) on leads 18, 20, and 22 of IMD 16 in order to monitorelectrical activity of heart 12, such as electrocardiogramdepolarizations of heart 12. In one example, the sensing module mayinclude a switch module to select which of the available electrodes onleads 18, 20, and 22 of IMD 16 are used to sense the heart activity.Additionally, the sensing module of IMD 16 may include multipledetection channels, each of which includes an amplifier, as well as ananalog-to-digital converter for digitizing the signal received from asensing channel for, e.g., electrogram signal processing by a processorof the IMD.

A telemetry module of IMD 16 may include any suitable hardware,firmware, software or any combination thereof for communicating withanother device, such as programmer 24. Under the control of a processorof IMD 16, the telemetry module may receive downlink telemetry from andsend uplink telemetry to programmer 24 with the aid of an antenna, whichmay be internal and/or external.

The various components of IMD 16 may be coupled to a power source, whichmay include a rechargeable or non-rechargeable battery. Anon-rechargeable battery may be capable of holding a charge for severalyears, while a rechargeable battery may be inductively charged from anexternal device, e.g., on a daily or weekly basis.

Leads 18, 20, 22 extend into the heart 12 of patient 14 to facilitatesensing of electrical activity of heart 12 and/or delivery of electricalstimulation to heart 12 by IMD 16, or to allow other sensors ortransducers attached to the leads to make measurements. In the exampleshown in FIG. 1, right ventricular (RV) lead 18 extends through one ormore veins (not shown), the superior vena cava (not shown), and rightatrium 26, and into right ventricle 28. Left ventricular (LV) coronarysinus lead 20 extends through one or more veins, the vena cava, rightatrium 26, and into the coronary sinus 30 to a region adjacent to thefree wall of left ventricle 32 of heart 12. Right atrial (RA) lead 22extends through one or more veins and the vena cava, and into the rightatrium 26 of heart 12.

System 10 also includes IMD 15, which includes a vascular sensor 38(FIG. 5). While referred to as including a vascular sensor, IMD 15 couldbe within a chamber of the heart, or generally within the circulatorysystem. In the illustrated example, IMD 15 is implanted in pulmonaryartery 39. In one example, IMD 15 is configured to sense blood pressureof patient 14. For example, IMD 15 may be arranged in pulmonary artery39 and be configured to sense the pressure of blood flowing from theright ventricle outflow tract (RVOT) from right ventricle 28 through thepulmonary valve to pulmonary artery 39. IMD 15 may therefore directlymeasure the pulmonary artery diastolic pressure (PAD) of patient 14. ThePAD value is a pressure value that can be employed in patientmonitoring. For example, PAD may be used as a basis for evaluatingcongestive heart failure in a patient.

In other examples, however, IMD 15 may be employed to measure bloodpressure values other than PAD. For example, IMD 15 may be arranged inright ventricle 28 of heart 14 to sense RV systolic or diastolicpressure. As shown in FIG. 1, IMD 15 is positioned in the main trunk ofpulmonary artery 39. In other examples, a sensor, such as IMD 15 may beeither positioned in the right or left pulmonary artery beyond thebifurcation of the pulmonary artery.

Moreover, the placement of IMD 15 is not restricted necessarily to thepulmonary side of the circulation. It could potentially be placed in thesystemic side of the circulation—e.g., under certain conditions and withappropriate safety measures, it could even be placed in the left atrium,left ventricle, or aorta. Additionally, IMD 15 is not restricted toplacement within the cardiovascular system. For example, the sensormight be placed in the renal circulation. IMD 15 placed in the renalcirculation may be beneficial, for example, in circumstances in whichIMD 16 is configured to treat heart failure based on some estimate ofthe degree of renal insufficiency in the patient derived from themonitoring of pressure or some other indication of renal circulation bythe sensor. In this or other non-cardiovascular examples, the sensor maystill communicate with IMD 16, or one or more sensors on leads 18, 20,or 22.

In some examples, IMD 15 includes a pressure sensor configured torespond to the absolute pressure inside pulmonary artery 39 of patient14. IMD 15 may be, in such examples, any of a number of different typesof pressure sensors. One form of pressure sensor that may be useful formeasuring blood pressure is a capacitive pressure sensor. Anotherexample pressure sensor is an inductive sensor. In some examples, IMD 15may also comprise a piezoelectric or piezoresistive pressure transducer.In some examples, IMD 15 may comprise a flow sensor.

In one example, IMD 15 comprises a leadless pressure sensor includingcapacitive pressure sensing elements configured to measure bloodpressure within pulmonary artery 39. As illustrated in FIGS. 1 and 2,IMD 15 may be in wireless communication with IMD 16 or one or moresensors on leads 18, 20, or 22, e.g., in order to transmit bloodpressure measurements to the IMD. IMD 15 may employ, e.g., radiofrequency (RF) or other telemetry techniques for communicating with IMD16 and other devices, including, e.g., programmer 24. In anotherexample, IMD 15 may include a tissue conductance communication (TCC)system by which the device employs tissue of patient 14 as an electricalcommunication medium over which to send and receive information to andfrom IMD 16 and other devices.

In some examples, IMD 15 may be implanted within other body lumens, suchas other vasculature of patient 14. Additionally or alternatively toincluding a pressure sensor, IMD 15 may also include sensors such as,but not limited to an electrocardiogram sensor, a fluid flow sensor, atissue oxygen sensor, an accelerometer, a glucose sensor, a potassiumsensor, a thermometer and/or other sensors. In some examples, system 10may include a plurality of sensors 38, e.g., to provide sensing of oneor more physiological conditions of patient 14 at a variety oflocations.

Referring again to FIG. 1, system 10 may, in some examples, additionallyor alternatively include one or more leads or lead segments (not shownin FIG. 1) that deploy one or more electrodes within the vena cava orother vein. These electrodes may allow alternative electrical sensingconfigurations that may provide improved or supplemental sensing in somepatients. Furthermore, in some examples, physiologicaltherapy/monitoring system 10 may include temporary or permanentepicardial or subcutaneous leads, instead of or in addition to leads 18,20 and 22. Such leads may be used for one or more of cardiac sensing,pacing, or cardioversion/defibrillation. Moreover, it is conceivablethat some sort of biodegradable fixation element could be used to holdIMD 15 to the epicardium, while a chronic fixation element fixes the IMD15 permanently in that location. Once fixed permanently, thebiodegradable fixation element would dissolve in a controlled fashion,leaving the IMD 15 permanently attached to the epicardium.

IMD 16 may sense electrical signals attendant to the depolarization andrepolarization of heart 12 via electrodes (not shown in FIG. 1) coupledto at least one of the leads 18, 20, 22. In some examples, IMD 16provides pacing pulses to heart 12 based on the electrical signalssensed within heart 12. The configurations of electrodes used by IMD 16for sensing and pacing may be unipolar or bipolar. IMD 16 may detectarrhythmia of heart 12, such as tachycardia or fibrillation ofventricles 28 and 32, and may also provide defibrillation therapy and/orcardioversion therapy via electrodes located on at least one of theleads 18, 20, 22. In some examples, IMD 16 may be programmed to delivera progression of therapies, e.g., pulses with increasing energy levels,until a fibrillation of heart 12 is stopped. IMD 16 detects fibrillationemploying any of a number of known fibrillation detection techniques.

In some examples, IMD 16 may also be solely a monitoring device,attached to various sensors, or even a monitoring device that onlycommunicates with one or more devices 38 in various locations of theheart, or other vasculature, or even other organs. Such a device couldbe used, for example, to provide an integrated physiologic monitoringsystem that monitors, e.g., heart failure and one or more of itscomorbidities (e.g. diabetes, renal function, etc.). Further, IMD 16could be a combined monitoring and therapy system with multiple sensorand or “remote” therapy devices, 38. For example, IMD 16 could control adevices, which may have similar outer housing dimensions, and may beimplanted similarly to IMD 15, but which are configured to act asleadless pacemakers, in the right and left ventricles, (or on the leftventricular epicardium), as a means of providing cardiacresynchronization. IMD 16 could then also communicate with other sensors38 in other vessels/organs, that serve primarily as sensors of flow,pressure, or other parameters, for the purpose of additional monitoringand control of heart failure. Heart failure is rapidly becoming viewedas a multi-system disease, which may affect the heart, lungs, kidneys,and pancreatic function.

Programmer 24 shown in FIG. 1 may be a handheld computing device,computer workstation, or networked computing device. Programmer 24 mayinclude electronics and other internal components necessary or desirablefor executing the functions associated with the device. In one example,programmer 24 includes one or more processors and memory, as well as auser interface, telemetry module, and power source. In general, memoryof programmer 24 may include computer-readable instructions that, whenexecuted by a processor of the programmer, cause it to perform variousfunctions attributed to the device herein. Memory, processor(s),telemetry, and power sources of programmer 24 may include similar typesof components and capabilities described above with reference to similarcomponents of IMD 16. The programmer may also be a dedicated wirelesssystem that communicates with IMD 16 remotely, say, from the patient'sbedside table, while the patient sleeps.

In one example, programmer 24 includes a user interface that receivesinput from a user. The user interface may include, for example, a keypadand a display, which may be, for example, a cathode ray tube (CRT)display, a liquid crystal display (LCD) or light emitting diode (LED)display. The keypad may take the form of an alphanumeric keypad or areduced set of keys associated with particular functions. Programmer 24can additionally or alternatively include a peripheral pointing device,such as a mouse, via which a user may interact with the user interface.In some examples, a display of programmer 24 may include a touch screendisplay, and a user may interact with programmer 24 via the display. Theuser may also interact with programmer 24 remotely via a networkedcomputing device. Or, the “programmer” may be a fully automatedmonitoring base station for use in the patient's home, with little or nocapability for the user to provide input or programming of the implanteddevice. A physician could also log into the programmer 24 from a remotelocation via the internet, cell phone technology, or othersatellite-based communication, and program the implanted device(s).

A user, such as a physician, technician, surgeon, electrophysiologist,or other clinician, may interact with programmer 24 to communicate withIMD 16. For example, the user may interact with programmer 24 toretrieve physiological or diagnostic information from IMD 16. A user mayalso interact with programmer 24 to program IMD 16, e.g., select valuesfor operational parameters of the IMD.

For example, the user may use programmer 24 to retrieve information fromIMD 16 regarding the rhythm of heart 12, trends therein over time,arrhythmic episodes, or sensor trends). As another example, the user mayuse programmer 24 to retrieve information from IMD 16 regarding othersensed physiological parameters of patient 14, such as intracardiac orintravascular pressure, activity, posture, respiration, or thoracicimpedance. The sensed physiological parameters may be based oninformation received from IMD 15. As another example, the user may useprogrammer 24 to retrieve information from IMD 16 regarding theperformance or integrity of IMD 16 or other components of system 10,such as leads 18, 20 and 22, or a power source of IMD 16. In someexamples, this information may be presented to the user as an alert.

The user may use programmer 24 to program a therapy progression, selectelectrodes used to deliver electrical stimulation to heart 12 (e.g., inthe form of pacing pulses or cardioversion or defibrillation shocks),select waveforms for the electrical stimulation, or select or configurea fibrillation detection algorithm for IMD 16. The user may also useprogrammer 24 to program aspects of other therapies provided by IMD 16,such as cardioversion or pacing therapies. In some examples, the usermay activate certain features of IMD 16 by entering a single command viaprogrammer 24, such as depression of a single key or combination of keysof a keypad or a single point-and-select action with a pointing device.

IMD 16 and programmer 24 may communicate via wireless communication,e.g. via telemetry modules in each of the devices using any number ofknown techniques. Examples of communication techniques may include, forexample, low frequency or RF telemetry, but other techniques are alsocontemplated. In some examples, programmer 24 may include a programminghead that may be placed proximate to the patient's body near the IMD 16implant site in order to improve the quality or security ofcommunication between IMD 16 and programmer 24. Other example medicalsystems need not have IMD 16 or provide therapy. For example, a medicalsystem may only include IMD 15, which may communicate directly with aneternal device, e.g., programmer 24.

FIG. 2 is a conceptual diagram illustrating IMD 16 and leads 18, 20 and22 of medical system 10 in greater detail. Leads 18, 20, 22 may beelectrically coupled to a signal generator, e.g., stimulation generator,and a sensing module of IMD 16 via connector block 34. In some examples,proximal ends of leads 18, 20, 22 may include electrical contacts thatelectrically couple to respective electrical contacts within connectorblock 34 of IMD 16. In addition, in some examples, leads 18, 20, 22 maybe mechanically coupled to connector block 34 with the aid of setscrews,connection pins, snap connectors, or another suitable mechanicalcoupling mechanism. Leads 18, 20 22 include electrodes for delivery ofstimulation and/or sensing and may additionally include one or moresensors as mentioned above with respect to FIG. 1.

Each of the leads 18, 20, 22 includes an elongated insulative lead body,which may carry a number of concentric coiled conductors separated fromone another by tubular insulative sheaths. Other lead configurations mayalso be used. Bipolar electrodes 40 and 42 are located adjacent to adistal end of lead 18 in right ventricle 28. In addition, bipolarelectrodes 44 and 46 are located adjacent to a distal end of lead 20 incoronary sinus 30 and bipolar electrodes 48 and 50 are located adjacentto a distal end of lead 22 in right atrium 26. In the illustratedexample, there are no electrodes located in left atrium 36. However,other examples may include electrodes in left atrium 36.

Electrodes 40, 44 and 48 may take the form of ring electrodes, andelectrodes 42, 46 and 50 may take the form of extendable helix tipelectrodes mounted retractably within insulative electrode heads 52, 54and 56, respectively. In other embodiments, one or more of electrodes42, 46 and 50 may take the form of small circular electrodes at the tipof a tined lead or other fixation element. Leads 18, 20, 22 also includeelongated electrodes 62, 64, 66, respectively, which may take the formof a coil. Each of the electrodes 40, 42, 44, 46, 48, 50, 62, 64 and 66may be electrically coupled to a respective one of the coiled conductorswithin the lead body of its associated lead 18, 20, 22, and therebycoupled to respective ones of the electrical contacts on the proximalend of leads 18, 20 and 22.

In some examples, IMD 16 includes one or more housing electrodes, suchas housing electrode 58, which may be formed integrally with an outersurface of hermetically-sealed housing 60 of IMD 16 or otherwise coupledto housing 60. In some examples, housing electrode 58 is defined by anuninsulated portion of an outward facing portion of housing 60 of IMD16. Other division between insulated and uninsulated portions of housing60 may be employed to define two or more housing electrodes. In someexamples, housing electrode 58 comprises substantially all of housing60. Housing 60 may enclose a signal generator that generates therapeuticstimulation, such as cardiac pacing pulses and defibrillation shocks, aswell as a sensing module for monitoring the rhythm of heart 12.

IMD 16 may sense electrical signals attendant to the depolarization andrepolarization of heart 12 via electrodes 40, 42, 44, 46, 48, 50, 62, 64and 66. The electrical signals are conducted to IMD 16 from theelectrodes via the respective leads 18, 20, 22. IMD 16 may sense suchelectrical signals via any bipolar combination of electrodes 40, 42, 44,46, 48, 50, 62, 64 and 66. Furthermore, any of the electrodes 40, 42,44, 46, 48, 50, 62, 64 and 66 may be used for unipolar sensing incombination with housing electrode 58. The sensed electrical signals maybe processed as a cardiac electrogram (EGM) signal by IMD 16.

Any combination of electrodes 40, 42, 44, 46, 48, 50, 58, 62, 64 and 66may be considered a sensing configuration that has one or moreelectrodes. In some examples, a sensing configuration may be a bipolarelectrode combination on the same lead, such as electrodes 40 and 42 oflead 18. In any sensing configuration, the polarity of each electrode inthe sensing configuration may be configured as appropriate for theapplication of the sensing configuration.

In some examples, IMD 16 delivers pacing pulses via bipolar combinationsof electrodes 40, 42, 44, 46, 48 and 50 to cause depolarization ofcardiac tissue of heart 12. In some examples, IMD 16 delivers pacingpulses via any of electrodes 40, 42, 44, 46, 48 and 50 in combinationwith housing electrode 58 in a unipolar configuration. Furthermore, IMD16 may deliver cardioversion or defibrillation pulses to heart 12 viaany combination of elongated electrodes 62, 64, 66, and housingelectrode 58. Electrodes 58, 62, 64, 66 may also be used to delivercardioversion pulses, e.g., a responsive therapeutic shock, to heart 12.Electrodes 62, 64, 66 may be fabricated from any suitable electricallyconductive material, such as, but not limited to, platinum, platinumalloy or other materials known to be usable in implantabledefibrillation electrodes.

The configuration of medical system 10 illustrated in FIGS. 1 and 2 ismerely one example. In other examples, a therapy system may includeepicardial leads and/or patch electrodes instead of or in addition tothe transvenous leads 18, 20, 22 illustrated in FIG. 1. Further, IMD 16need not be implanted within patient 14. In examples in which IMD 16 isnot implanted in patient 14, IMD 16 may deliver defibrillation pulsesand other therapies to heart 12 via percutaneous leads that extendthrough the skin of patient 14 to a variety of positions within oroutside of heart 12.

In addition, in other examples, a therapy system may include anysuitable number of leads coupled to IMD 16, and each of the leads mayextend to any location within or proximate to heart 12. For example,other examples of therapy systems may include three transvenous leadslocated as illustrated in FIGS. 1 and 2, and an additional lead locatedwithin or proximate to left atrium 36. As another example, otherexamples of therapy systems may include a single lead that extends fromIMD 16 into right atrium 26 or right ventricle 28, or two leads thatextend into a respective one of the right ventricle 26 and right atrium26.

FIG. 3 is a conceptual diagram illustrating an example medical system 11that may be used to monitor one or more physiological parameters ofpatient 14 and/or to provide therapy to heart 12 of patient 14. Medicalsystem 11 includes IMD 17, which is coupled to programmer 24. IMD 17 maybe an implantable leadless pacemaker that provides electrical signals toheart 12 via one or more electrodes (not shown in FIG. 3) on its outerhousing. Additionally or alternatively, IMD 17 may sense electricalsignals attendant to the depolarization and repolarization of heart 12via electrodes on its outer housing. In some examples, IMD 17 providespacing pulses to heart 12 based on the electrical signals sensed withinheart 12.

IMD 17 includes a set of active fixation tines to secure IMD 17 to apatient tissue. In other examples, IMD 17 may be secured with othertechniques such as a helical screw or with an expandable fixationelement. In the example of FIG. 3, IMD 17 is positioned wholly withinheart 12 proximate to an inner wall of right ventricle 28 to provideright ventricular (RV) pacing. Although IMD 17 is shown within heart 12and proximate to an inner wall of right ventricle 28 in the example ofFIG. 3, IMD 17 may be positioned at any other location outside or withinheart 12. For example, IMD 17 may be positioned outside or within rightatrium 26, left atrium 36, and/or left ventricle 32, e.g., to provideright atrial, left atrial, and left ventricular pacing, respectively.

Depending on the location of implant, IMD 17 may include otherstimulation functionalities. For example, IMD 17 may provideatrioventricular nodal stimulation, fat pad stimulation, vagalstimulation, or other types of neurostimulation. In other examples, IMD17 may be a monitor that senses one or more parameters of heart 12 andmay not provide any stimulation functionality. In some examples, medicalsystem 11 may include a plurality of leadless IMDs 17, e.g., to providestimulation and/or sensing at a variety of locations.

As mentioned above, IMD 17 includes a set of active fixation tines. Theactive fixation tines in the set are deployable from a spring-loadedposition in which distal ends of the active fixation tines point awayfrom the IMD to a hooked position in which the active fixation tinesbend back towards the IMD. The active fixation tines allow IMD 17 to beremoved from a patient tissue followed by redeployment, e.g., to adjustthe position of IMD 17 relative to the patient tissue. For example, aclinician implanting IMD 17 may reposition IMD 17 during an implantationprocedure if the original deployment of the active fixation tinesprovides an insufficient holding force to reliably secure IMD 17 to thepatient tissue. As another example, the clinician may reposition IMD 17during an implantation procedure if testing of IMD 17 indicates anunacceptably high capture threshold, which may be caused by, e.g., thespecific location of IMD 17 or a poor electrode-tissue connection.

FIG. 3 further depicts programmer 24 in wireless communication with IMD17. In some examples, programmer 24 comprises a handheld computingdevice, computer workstation, or networked computing device. Programmer24 includes a user interface that presents information to and receivesinput from a user. The user may also interact with programmer 24remotely via a networked computing device.

A user, such as a physician, technician, surgeon, electrophysiologist,other clinician, or patient, interacts with programmer 24 to communicatewith IMD 17. For example, the user may interact with programmer 24 toretrieve physiological or diagnostic information from IMD 17. A user mayalso interact with programmer 24 to program IMD 17, e.g., select valuesfor operational parameters of the IMD 17. For example, the user may useprogrammer 24 to retrieve information from IMD 17 regarding the rhythmof heart 12, trends therein over time, or arrhythmic episodes.

As an example, the user may use programmer 24 to retrieve informationfrom IMD 17 regarding other sensed physiological parameters of patient14 or information derived from sensed physiological parameters, such asintracardiac or intravascular pressure, intracardiac or intravascularfluid flow, activity, posture, tissue oxygen levels, respiration, tissueperfusion, heart sounds, cardiac electrogram (EGM), intracardiacimpedance, or thoracic impedance. In some examples, the user may useprogrammer 24 to retrieve information from IMD 17 regarding theperformance or integrity of IMD 17 or other components of system 17, ora power source of IMD 17. As another example, the user may interact withprogrammer 24 to program, e.g., select parameters for, therapiesprovided by IMD 17, such as pacing and, optionally, neurostimulation.

IMD 17 and programmer 24 may communicate via wireless communicationusing any techniques known in the art. Examples of communicationtechniques may include, for example, low frequency or radiofrequency(RF) telemetry, but other techniques are also contemplated. In someexamples, programmer 24 may include a programming head that may beplaced proximate to the patient's body near the IMD 17 implant site inorder to improve the quality or security of communication between IMD 17and programmer 24.

FIG. 4 illustrates leadless IMD 17 of FIG. 3 in further detail. In theexample of FIG. 4, leadless IMD 17 includes tine fixation subassembly100 and electronic subassembly 150. Tine fixation subassembly 100includes active fixation tines 103 and is configured to deploy anchorleadless IMD 17 to a patient tissue, such as a wall of heart 12.

Electronic subassembly 150 includes electrode 123, control electronics152, which controls the sensing and/or therapy functions of IMD 17, andbattery 160, which powers control electronics 152. As one example,control electronics 152 may include sensing circuitry, a stimulationgenerator and a telemetry module. As one example, battery 160 maycomprise features of the batteries disclosed in U.S. patent applicationSer. No. 12/696,890, titled IMPLANTABLE MEDICAL DEVICE BATTERY and filedJan. 29, 2010, the entire contents of which are incorporated byreference herein.

The housings of control electronics 152 and battery 160 are formed froma biocompatible material, such as a stainless steel or titanium alloy.In some examples, the housings of control electronics 152 and battery160 may include a parylene coating. Electronic subassembly 150 furtherincludes anode 162, which may include a titanium nitride coating. Theentirety of the housings of control electronics 152 and battery 160 areelectrically connected to one another, but only anode 162 isuninsulated. Alternatively, anode 162 may be electrically isolated fromthe other portions of the housings of control electronics 152 andbattery 160. In other examples, the entirety of the housing of battery160 or the entirety of the housing of electronic subassembly 150 mayfunction as an anode instead of providing a localized anode such asanode 162.

Delivery tool interface 158 is located at the proximal end of electronicsubassembly 150. Delivery tool interface 158 is configured to connect toa delivery device, such as a catheter used to position IMD 17 during animplantation procedure. For example, delivery tool interface 158represents a looped element of IMD 17 and may be engaged by a catheterduring delivery as discussed herein with respect to a variety ofdifferent examples.

Active fixation tines 103 are deployable from a spring-loaded positionin which distal ends 109 of active fixation tines 103 point away fromelectronic subassembly 150 to a hooked position in which active fixationtines 103 bend back towards electronic subassembly 150. For example,active fixation tines 103 are shown in a hooked position in FIG. 4.Active fixation tines 103 may be fabricated of a shape memory material,which allows active fixation tines 103 to bend elastically from thehooked position to the spring-loaded position. As an example, the shapememory material may be shape memory alloy such as Nitinol.

In some examples, all or a portion of tine fixation subassembly 100,such as active fixation tines 103, may include one or more coatings. Forexample, tine fixation subassembly 100 may include a radiopaque coatingto provide visibility during fluoroscopy. In one such example, activefixation tines 103 may include one or more radiopaque markers. Asanother example, active fixation tines 103 may be coated with a tissuegrowth promoter or a tissue growth inhibitor. A tissue growth promotermay be useful to increase the holding force of active fixation tines103, whereas a tissue growth inhibitor may be useful to facilitateremoval of IMD 17 during an explantation procedure, which may occur manyyears after the implantation of IMD 17.

As one example, IMD 17 and active fixation tines 103 may comprisefeatures of the active fixation tines disclosed in U.S. Provisional Pat.App. No. 61/428,067, titled, “IMPLANTABLE MEDICAL DEVICE FIXATION” andfiled Dec. 29, 2010, the entire contents of which are incorporated byreference herein.

FIG. 5 illustrates leadless IMD 15, which includes sensor element 38 andexpandable fixation element 41. Expandable fixation element 41 isconfigured for securing leadless IMD 15 within a vasculature.

Expandable fixation element 41 is configured such that the outerdiameter of expandable fixation element 41 is expandable to provide aninterference fit with the inner diameter of pulmonary artery 39, orother body lumen. In some examples, expandable fixation element 41 maybe partially deployable. As an example, the distal end of expandablefixation element 41 may be deployed from a catheter and expanded toprovide an interference fit with the body lumen while the proximal endof expandable fixation element 41 may remain in a collapsed positionwithin the distal end of the catheter.

Expandable fixation element 41 allows IMD 15 to be retracted beforefully deploying IMD 15, e.g., to adjust the position of IMD 15 with avasculature to a location in the vasculature providing a tighter (orlooser) interference fit. For example, a clinician implanting IMD 15 mayreposition IMD 15 during an implantation procedure if partial deploymentof expandable fixation element 41 provides an insufficient holding forceindicating that full deployment of expandable fixation element 41 maynot reliably secure IMD 15 within the vasculature. As another example, aclinician may select an expandable fixation element with a size bettersuited for the vasculature than expandable fixation element 41 thatprovided an insufficient holding force.

Sensor element 38 includes control electronics that control the sensingand/or therapy functions of IMD 15 and a battery that powers the controlelectronics. As one example, the control electronics may include sensingcircuitry and a telemetry module. Moreover, the battery may comprisefeatures of the batteries disclosed in U.S. patent application Ser. No.12/696,890, titled IMPLANTABLE MEDICAL DEVICE BATTERY and filed Jan. 29,2010, the contents of which were previously incorporated by referenceherein. The housing of sensor element 38 may be formed from abiocompatible material, such as stainless steel and/or titanium alloys.

Expandable fixation element 41 may be fabricated of a shape memorymaterial that allows expandable fixation element 41 to bend elasticallyfrom the collapsed position to the expanded position. As an example, theshape memory material may be shape memory alloy such as Nitinol. As anexample, expandable fixation element 41 may store less potential energyin the expanded position and thus be naturally biased to assume theexpanded position when in the collapsed position. In this manner,expandable fixation element 41 may assume an expanded position when nolonger constrained by a catheter or other delivery device.

In some examples, expandable fixation element 41 may resemble a stent.Techniques for a partially deployable stents that may be applied toexpandable fixation element 41 are disclosed in U.S. Pat. Pub. No.2007/0043424, titled, “RECAPTURABLE STENT WITH MINIMUM CROSSING PROFILE”and dated Feb. 22, 2007, the entire contents of which are incorporatedby reference herein, as well as U.S. Pat. Pub. No. 2009/0192585, titled,“DELIVERY SYSTEMS AND METHODS OF IMPLANTATION FOR PROSTETIC HEARTVALVES” and dated Jul. 30, 2009, the entire contents of which are alsoincorporated by reference herein.

In some examples, all or a portion of expandable fixation element 41,may include one or more coatings. For example, expandable fixationelement 41 may include a radiopaque coating to provide visibility duringfluoroscopy. As another example, expandable fixation element 41 may becoated with a tissue growth promoter or a tissue growth inhibitor.

FIGS. 6-8E illustrate a system for intravascular delivery of an IMDduring an implantation procedure. As referred to herein, intravascularIMD delivery not only includes delivering IMD through a vasculature to atarget site within a vasculature, but also includes delivering IMDthrough a vasculature to other target sites such as target sites withinthe heart and other transvascular IMD deliveries. The kit of the IMDdelivery system includes assembly 201 and assembly 221, shown in FIGS. 6and 7 respectively. As shown in FIG. 6, assembly 201 includes elongatedinner sheath 202 and coupling module 206, which is slidably connected toinner sheath 202. As shown in FIG. 7, assembly 221 includes elongatedouter sheath 234 and coupling module 226.

Outer sheath 234 of assembly 221 forms an inner lumen 227 (FIG. 8A) withproximal opening 233 (FIG. 8A) and distal opening 235 (FIG. 7). Outersheath 234 is sized to traverse a vasculature of a patient during asurgical procedure to facilitate positioning distal opening 235proximate a target site within the patient. In different examples, outersheath 234 may be steerable or be configured to traverse a guidewire tobe directed to the target site from the access point of the vasculature.In any event, outer sheath 234 includes sufficient longitudinalstiffness to facilitate manipulation from its proximal end, but alsoinclude sufficient radial flexibility to facilitate following thepatient's vasculature from an access point, such as a femoral artery, toa position proximate the target site within the patient.

In one example, outer sheath 234 may have an inner diameter of about0.15 inch and an outer diameter of about 0.18 inch. It may be extrudedfrom polyether block amide copolymer (PEBA) having 55 shore D durometeror, alternatively, may be formed as a reinforced tube having an innerpolytetrafluoroethylene (PTFE) liner, an intermediate reinforcing layerof braided stainless steel and an outer jacket of 55D durometer PEBA. Inother examples, other flexible polymers may be used such as nylons andpolyethylenes. The distal end of outer sheath 234 preferably includes aradiopaque ring that may be formed by incorporating barium sulfate orother suitable radiopaque material such as tungsten into or at the endof outer sheath 234.

During an implantation procedure, the distal end of outer sheath 234 ispositioned proximate a target site for implantation of the IMD. Innerlumen 227 is configured to receive the distal end of inner sheath 202,as well as IMD 214, and inner sheath 202 is used to push the IMD throughthe entirety outer sheath 234 to the target site. In this manner, an IMDis passed through the entirety of the inner lumen 227 before exitingdistal opening 235 of outer sheath 234 during the implantationprocedure.

In assembly 221, coupling module 226 is secured to the proximal end ofouter sheath 234. Coupling module 226 includes valve 230, which isconfigured to prevent bodily fluids from passing through inner lumen 227and leaking out of proximal opening 233. Coupling module 226 furtherincludes Luer fitting 232 that facilitates flushing outer sheath 234.

Coupling module 226 is configured to connect to coupling module 206 ofassembly 201 such that inner sheath 202 is axially aligned with outersheath 234. For example, coupling modules 206, 226 include quick connectfeatures for mating coupling module 226 with coupling module 206 suchthat inner sheath 202 is in coaxial alignment with outer sheath 234. Inthe example, shown in FIG. 6, the quick connect features of couplingmodule 206 are grooves 208, which are configured to receive protrusions228 of coupling module 226 in a rotating snap-fit configuration. Itshould be noted, however, that the particular techniques used for matingcoupling module 206 with coupling module 226 are not germane to thisdisclosure, and any suitable connecting features, such as snap-fit orthreaded features may be used in other examples.

As previously mentioned, elongated inner sheath 202 is slidablyconnected to inner sheath 202 as part of assembly 201. This allows innersheath 202 to enter proximal opening 233 of inner lumen 227 of outersheath 234 once coupling module 206 is mated to coupling module 226 suchthat inner sheath 202 is in coaxial alignment with outer sheath 234. Inone example, outer sheath 234 may have an inner diameter of about 0.15inches and the distal end of inner sheath may have an outer diameter ofabout 0.12-0.14 inches at its distal end. In some examples, inner sheath202 may have a smaller profile along its length than at its distal end,e.g., a tighter fitting distal cap to enable a good pushing surface withlower proximal friction due to the smaller profile along the length ofinner sheath 202. In addition or alternately, inner sheath 202 may beshaped with a lower contact friction design such as a triangular to starlike profile to minimize drag friction with outer sheath 234. Indifferent examples, inner sheath may have a solid profile, a hollowtubular profile or a combination thereof.

In some examples, inner sheath may be formed from 70D durometer PEBA. Inother examples, other flexible polymers may be used such as nylons andpolyethylenes.

Inner sheath 202 includes finger grip 204, which allow a clinician toslidably move sheath 202 relative to coupling module 206 and outersheath 234 during an implantation procedure. In some examples, innerlumen 227 of outer sheath 234 and/or the outer surface of inner sheath202 may include a friction-reducing coating to reduce the force requiredto move inner sheath within inner lumen 227 of outer sheath 234.Coupling module 206 further includes seal 210 (FIGS. 8A-8C), whichcreates a seal between coupling module 206 and inner sheath 202 whileallowing inner sheath 202 to slide in a longitudinal direction.

FIGS. 8A-8E illustrate techniques for intravascular implantation of IMD214 using a kit including assemblies 201, 221. FIGS. 8A-8E illustrateassemblies 201, 221 as well as IMD 214. IMD 214 includes expandablefixation element 215, which is deployable from a collapsed position toan expanded position secure the IMD 214 proximate a target site within apatient.

While FIGS. 8A-8E illustrate implantation techniques using IMD 214, indifferent examples, IMD 214 may be substantially similar to IMD 17 (FIG.4) or IMD 15 (FIG. 5). As one example, the intravascular IMD deliverysystem of FIGS. 6-8E may be used to deliver IMD 17 to a position withina heart of a patient, such as a position proximate to an inner wall ofthe right ventricle, within the right atrium, the left atrium, and/orleft ventricle. As another example, the intravascular IMD deliverysystem of FIGS. 6-8E may be used to deliver IMD 15 to an intravascularposition such as a pulmonary artery or other vasculature of the patient.

As shown in FIGS. 8A-8E, coupling module 206 of assembly 201 isconfigured to mate to coupling module 226 of assembly 221 to facilitateintravascular implantation of IMD 214 within a patient. During animplantation procedure, the clinician would position the distal end ofouter sheath 234 proximate to a target site within the patient via avasculature accessed during a surgical procedure. For example, outersheath 234 may be advanced into an entry vessel, such as the femoralartery, and then manipulated and navigated through the patient'svasculature until the distal end of outer sheath 234 proximate to atarget site within the patient. The clinician may use imagingtechniques, such as fluoroscopy, to monitor the position of outer sheath234, inner sheath 202, and IMD 214 throughout the implantationprocedure. Assemblies 201, 221 and/or IMD 214 may include radiopaqueportions or markers to facilitate visualization.

Once the distal end of outer sheath 234 is proximate to a target sitewithin the patient, as shown in FIG. 8A, a clinician positions assembly201 adjacent to assembly 221 such that coupling module 206 facescoupling module 221. Then, as shown in FIG. 8B, coupling module 206 ismated to coupling module 226 such that inner sheath 202 is in coaxialalignment with outer sheath 234.

Coupling module 206 forms inner lumen 207, which is configured to holdIMD 214 when coupling module 206 is not connected coupling module 226.When coupling module 206 is mated to coupling module 226, couplingmodule 206 presses open the leaflets of valve 230 such that inner lumen207 of coupling module 206 opens to inner lumen 227 of outer sheath 234.

In this manner, valve 230 is configured to open to allow inner sheath202 to enter inner lumen 227 of outer sheath 234. In addition, couplingmodule 206 forms a seal with coupling module 226 when coupling module206 is connected to coupling module 226. Even though valve 230 is openwhen coupling module 206 is connected to coupling module 226, the sealbetween coupling module 206 and coupling module 226 and seal 210 betweeninner sheath 202 coupling module 206 combine to prevent bodily fluidsfrom continuously exiting the patient through inner lumen 227 of outersheath 234.

As shown in FIG. 8C, a clinician uses inner sheath 202 to push IMD 214into proximal opening 233 of inner lumen 227 of outer sheath 234. Forexample, IMD 214 may be preloaded within inner lumen 207 of couplingmodule 206 in assembly 201 before coupling module 206 is mated tocoupling module 226. In the example in which IMD 214 includes a pressuresensor, such as a pressure transducer, preloading IMD 214 within innerlumen 207 by the manufacturer may serve to protect the transducer fromdamage, such as damage caused by handling. By pushing on finger grip 204(FIG. 6), the clinician may slide inner sheath 202 in a longitudinaldirection to push IMD 214 out of inner lumen 207 of coupling module 206and into inner lumen 227 of outer sheath 234.

As shown in FIG. 8D, the clinician may continue push IMD 214 throughinner lumen 227 of outer sheath 234 advancing IMD 214 through thepatient's vasculature as navigated by outer sheath 234. FIG. 8Dillustrates inner sheath 202 pushing IMD 214 up to distal opening 235 ofouter sheath 234. FIG. 8E illustrates inner sheath 202 pushing IMD 214through distal opening 235 of outer sheath 234. As shown in FIG. 8E,expandable fixation element 215 of IMD 214 is expanded from a collapsedposition to an expanded position as IMD 214 through distal opening 235.In the expanded position, expandable fixation element 215 will secureIMD 214 within the patient, e.g., as described with respect to IMD 17(FIG. 4) or IMD 15 (FIG. 5).

The IMD delivery system of FIGS. 6-8E may provide one or moreadvantages. As one example, intravascular delivery of larger implantsmay often necessitate large bore delivery sheaths to be tracked throughcomplex anatomy, which can require a clinician to use a variety ofspecialized tools. As compared to an intravascular delivery system inwhich an IMD is delivered to a target site simultaneously with thedelivery system, e.g., the IMD is contained in the distal end of thedelivery system as the delivery system is routed to the target site, theIMD delivery system of FIGS. 6-8E may simplify routing of the deliverysystem to the target site. For example, with the IMD delivery system ofFIGS. 6-8E, the clinician first routes outer sheath 234 to the targetsite. As clinicians often have experience routing intravascular sheaths,the process and instruments used to route outer sheath 234 may befamiliar to the clinician. Furthermore, with the IMD delivery system ofFIGS. 6-8E, only after first routing outer sheath 234 to the targetsite, does the clinician then introduce the IMD. This may reduce thechance for damage to the IMD as compared to a delivery system in whichthe IMD is transported proximate to the target site within the distalportion of the delivery system.

FIGS. 9A-9D illustrate example techniques for intravascular delivery ofa sheath. As one example, the techniques illustrated in FIGS. 9A-9D maybe used for intravascular delivery of outer sheath 234. In such anexample, outer sheath 320 of FIGS. 9A-9D may be considered to besubstantially similar to outer sheath 234. For example, outer sheath 320may be included in an assembly with coupling module 206, and outersheath 320 may be used to deliver an IMD as described with respect toFIGS. 8A-8E. However, the techniques illustrated in FIGS. 9A-9D are notthe only manner in which outer sheath 234 may be delivered within apatient and any technique known to those in the art for intravasculardelivery of a sheath may be used to position outer sheath 234.

As represented by FIG. 9A, guidewire 310 is first routed from an accesspoint through a vasculature of the patient until distal end 312 ofguidewire 310 is positioned proximate to a target site within thepatient. In different examples, the target site may be within apulmonary artery of the patient, within another vasculature of thepatient, or a position within a heart of a patient, such as a positionproximate to an inner wall of the right ventricle, right atrium, leftatrium, and/or left ventricle. Guidewire 310 may be routed using anytechniques known to those in the art. For example, clinician may useimaging techniques, such as fluoroscopy, to monitor the position ofguidewire 310.

As represented by FIG. 9B, after distal end 312 of guidewire 310 ispositioned proximate to a target site within the patient, the clinicianroutes an assembly including outer sheath 320 and inner sheath 330 overthe proximal end guidewire 310 and pushes the assembly along guidewire310 until distal opening 322 of outer sheath 320 is proximate the targetsite within the patient.

Elongated outer sheath 320 is sized to traverse the vasculature of thepatient. Outer sheath 320 forms inner lumen 324, which has distalopening 322. In some examples, inner lumen 324 may extend the length ofouter sheath 320 and also provide a proximal opening.

Elongated inner sheath 330 includes tapered distal end 332. In oneexample, tapered distal end 332 may have a conical shape. Tapered distalend 332 is configured to substantially fill inner lumen 324 of outersheath 320 to close-off distal opening 322 of outer sheath 320. Innersheath 330 includes guidewire lumen 334, which may extend throughout thelength of inner sheath 330. The diameter of guidewire lumen 334 atdistal tip 332 corresponds to the diameter of guidewire 310. In someexamples, guidewire lumen 334 may be greater at other portions of innersheath 330 than at distal tip 332, and such a configuration may limitfriction between guidewire 310 and inner sheath 330. In other examples,guidewire lumen 334 may have a consistent diameter throughout the lengthof inner sheath 330. In one example, distal tip 332 may be formed from35D durometer PEBA or a blend of 40D durometer PEBA and barium sulfate,bismuth compounds (trioxide, oxychloride), tungsten and/or polymerfillers. In other examples, other flexible polymers may be used such asnylons and polyethylenes. In any case, these and other polymer fillersmay be selected to provide desirable material properties, such asstiffness, flexibility, reduce friction and/or increase radiopacity.

In the assembly of outer sheath 320 and inner sheath 330, tapered distalend 332 extends beyond distal opening 322 of outer sheath 320; however,inner sheath 330 may be advanced and retracted relative to outer sheath320 by the clinician during the implantation procedure, if desired, asinner sheath 330 is slidable within inner lumen 324 of outer sheath 320.

After the assembly of outer sheath 320 and inner sheath 330 is advancedalong guidewire 310 until distal opening 322 of outer sheath 320 isproximate the target site within the patient (FIG. 9C), guidewire 310and inner sheath 330 are withdrawn from outer sheath 320 (FIG. 9D). Forexample, a clinician may simply pull on guidewire 310 and inner sheath330 from a proximal end of outer sheath 320 to slide guidewire 310 andinner sheath 330 out of the proximal opening of outer sheath 320. Inanother example, a clinician may remove inner sheath 330 and leave theguidewire 312 in place to enable the tracking of ancillary devices.

FIGS. 10A-10D illustrate example techniques for intravascular deliveryof IMD 380 through outer sheath 320 using deployment receptacle 340.Specifically, FIGS. 10A-10D illustrate distal portions of outer sheath320 and elongated deployment receptacle 340. As previously mentioned,outer sheath 320 may be considered to be substantially similar to outersheath 234. For example, outer sheath 320 may be included in an assemblywith coupling module 206. In such an example, deployment receptacle 340may be slidably coupled to coupling module 226 in a mating assembly, andthe distal end of deployment receptacle 340 may be positioned proximatea target site within a patient in a similar manner that inner sheath 202is positioned proximate a target site within a patient as described withrespect to FIGS. 8A-8E.

Deployment receptacle 340 includes deployment bay 342 at a distal end ofdeployment receptacle 340. Deployment bay 342 is configured to carry IMD380 through inner lumen 324 of outer sheath 320. Deployment receptacle340 is slidable within inner lumen 324 of outer sheath 320 when innerlumen 324 is open, e.g., when inner sheath 330 is not within inner lumen324 of outer sheath 320.

IMD 380 includes expandable fixation element 381, which is deployablefrom a collapsed position to an expanded position secure the IMD 380proximate a target site within a patient. While FIGS. 10A-10D illustrateimplantation techniques using IMD 380, in different examples, IMD 380may be substantially similar to IMD 17 (FIG. 4) or IMD 15 (FIG. 5). Asone example, the techniques of FIGS. 10A-10D may be used to deliver IMD17 to a position within a heart of a patient, such as a positionproximate to an inner wall of the right ventricle, within the rightatrium, the left atrium, and/or left ventricle. As another example, thetechniques of FIGS. 10A-10D may be used to deliver IMD 15 to anintravascular position such as a pulmonary artery or other vasculatureof the patient.

Deployment receptacle 340 facilitates deployment of IMD 380 out ofdistal opening 322 of outer sheath 320. In particular, deploymentreceptacle 340 includes tether 350, which has helical element 352 on itsdistal end. Tether 350 is remotely controllable from a proximal end ofdeployment receptacle 340 to release IMD 380 from deployment bay 342.Tether 350 is stiff enough to facilitate pushing IMD 380 out ofdeployment bay 342 as well as pushing IMD 380 into deployment bay 342.

Specifically, a clinician, from the proximal end of deploymentreceptacle 340, may remotely push tether 350 distally relative todeployment bay 342 to push IMD 380 out distal opening 343 of deploymentbay 342. This maintains the position of IMD 380 within the patientduring deployment, which facilitates precise positioning of IMD 380. Inone example, clinician actually retracts outer sheath 320 proximally topush tether 350 distally relative to deployment bay 342 to push IMD 380out distal opening 343 of deployment bay 342. Then the clinician may,again from the proximal end of deployment receptacle 340, remotelyrotate tether 350 such that helical element 352 releases a loopedelement of IMD 380 to deploy IMD 380. Specifically, in the exampleillustrated in FIG. 10C, as expandable fixation element 381 is thelooped element of IMD 380, and rotating helical element 352 releasesexpandable fixation element 381 from deployment receptacle 340.

During an implantation procedure, the clinician would position thedistal end of outer sheath 320 proximate to a target site within thepatient via a vasculature accessed during a surgical procedure. Forexample, outer sheath 320 may be advanced into an entry vessel, such asthe femoral artery, and then manipulated and navigated through thepatient's vasculature until the distal end of outer sheath 320 proximateto a target site within the patient. The clinician may use imagingtechniques, such as fluoroscopy, to monitor the position of outer sheath320, deployment receptacle 340, and IMD 380 throughout the implantationprocedure. In some examples, may be outer sheath 320 routed to thetarget site using the techniques described with respect to FIGS. 9A-9D;however, any technique known to those in the art for intravasculardelivery of a sheath may be position outer sheath 234 such that thedistal end of outer sheath 320 is proximate the target site within thepatient.

Once the distal end of outer sheath 320 proximate to a target sitewithin the patient, as represented by FIG. 10A, a clinician delivers IMD380 to the target site by pushing deployment receptacle 340 throughinner lumen 324 of outer sheath 320. In one example, the clinician mayalign distal opening 343 of deployment receptacle 340 with the proximalopening of inner lumen 324 of outer sheath 320. As an example, IMD 380may be preloaded within deployment bay 342 before deployment receptacle340 is inserted into outer sheath 320. In the example in which IMD 380includes a pressure sensor, such as a pressure transducer, preloadingIMD 380 within deployment bay 342 by the manufacturer may serve toprotect the transducer from damage, such as damage caused by handling.The clinician continues to push deployment receptacle 340 through innerlumen 324 of outer sheath 320 at least until distal opening 343 ofdeployment receptacle 340 reaches distal opening 322 of outer sheath320.

As represented by FIG. 10B, once deployment bay 342 is positionedproximate the target site, the clinician deploys IMD 380 from deploymentreceptacle 340. Specifically, a clinician, from the proximal end ofdeployment receptacle 340, may remotely push tether 350 distallyrelative to deployment bay 342 to push IMD 380 out distal opening 343 ofdeployment bay 342. As shown in FIG. 10B, a portion of expandablefixation element 381 of IMD 380 is expanded from a collapsed position toan expanded position as IMD 380 passes out of distal opening 343 ofdeployment bay 342. In the expanded position, expandable fixationelement 381 will secure IMD 380 within the patient, e.g., as describedwith respect to IMD 17 (FIG. 4) or IMD 15 (FIG. 5).

As represented by FIG. 10C, once IMD 380 is fully removed fromdeployment bay 342, expandable fixation element 381 of IMD 380 isexpanded assumes the expanded position. In order to fully deploy IMD 380from deployment receptacle 340, the clinician remotely rotates tether350 such that helical element 352 releases expandable fixation element381, as represented by FIG. 10D. At this point, IMD 380 is fullydeployed proximate to the target site, e.g., within a vasculature of thepatient. IMD 380 is engaged to the vasculature of the patient becausethe expandable fixation element 381 elastically compressed withindeployment receptacle 340 and expands to engage vasculature of thepatient once released from deployment receptacle 340.

The clinician may optionally recapture IMD 380 by first grabbing alooped element of IMD 380, e.g., expandable fixation element 381, withhelical element 352, and then using tether 350 to pull IMD 380 intodeployment bay 342. In one example, tether 350 is held in a fixedlocation while outer sheath 320 is advanced distally to pull IMD 380into deployment bay 342. In this manner, deployment receptacle 340 maybe used to adjust the position of IMD 380 after full deployment, or toremove IMD 380 from the patient after full deployment. As one example,the clinician may decide to remove IMD 380 from the patient after fulldeployment if electronic testing of IMD 380 produces unsatisfactoryresults. As another example, the clinician may decide to remove IMD 380from the patient after full deployment if the clinician determines thatexpandable fixation element 381 is improperly sized to locate IMD 380 atthe target site. In such an example, IMD 380 may be replaced with an IMDincluding an expandable fixation element with a proper size. As anotherexample, a clinician may use deployment receptacle 340 to remove IMD 380during a subsequent surgical procedure, e.g., once IMD 380 has met orexceeded its projected lifespan. During such a subsequent surgicalprocedure, IMD 380 could be replaced with a new IMD using the same outersheath used during the removal of IMD 380.

FIGS. 11A-11D illustrate example techniques for intravascular deliveryof sheath 420 using inner sheath 430, which includes a distal portionwith inflatable member 432. As one example, the techniques illustratedin FIGS. 11A-11D may be used for intravascular delivery of outer sheath234. In such an example, outer sheath 420 of FIGS. 11A-11D may beconsidered to be substantially similar to outer sheath 234. For example,outer sheath 420 may be included in an assembly with coupling module206, and outer sheath 420 may be used to deliver an IMD as describedwith respect to FIGS. 8A-8E.

As represented by FIG. 11A, guidewire 410 is first routed from an accesspoint through a vasculature of the patient until distal end 412 ofguidewire 410 is positioned proximate to a target site within thepatient. In different examples, the target site may be within apulmonary artery of the patient, within another vasculature of thepatient, or a position within a heart of a patient, such as a positionproximate to an inner wall of the right ventricle, right atrium, leftatrium, and/or left ventricle. Guidewire 410 may be routed using anytechniques known to those in the art. For example, clinician may useimaging techniques, such as fluoroscopy, to monitor the position ofguidewire 410.

As represented by FIG. 11B, after distal end 412 of guidewire 410 ispositioned proximate to a target site within the patient, the clinicianroutes an assembly including outer sheath 420 and inner sheath 430 overthe proximal end guidewire 410 and pushes the assembly along guidewire410 until distal opening 422 of outer sheath 420 is proximate the targetsite within the patient.

Elongated outer sheath 420 is sized to traverse the vasculature of thepatient. Outer sheath 420 forms inner lumen 424, which has distalopening 422. In some examples, inner lumen 424 may extend the length ofouter sheath 420 and also provide a proximal opening.

Elongated inner sheath 430 includes inflatable member 432. Inflatablemember 432 is selectively inflatable from a proximal end of inner sheath430. When inflated inflatable member 432 is configured to substantiallyfill inner lumen 424 of outer sheath 420 and close-off distal opening422 of outer sheath 420.

Inner sheath 430 includes guidewire lumen 434, which may extendthroughout the length of inner sheath 430. The diameter of guidewirelumen 434 at the distal portion of inner sheath 430 corresponds to thediameter of guidewire 410. In some examples, guidewire lumen 434 may begreater at other portions of inner sheath 430 than at the distal portionof inner sheath 430. Such a configuration may limit friction betweenguidewire 410 and inner sheath 430. In other examples, guidewire lumen434 may have a consistent diameter throughout the length of inner sheath430.

In the assembly of outer sheath 420 and inner sheath 430, inflatablemember 432 extends beyond distal opening 422 of outer sheath 420;however, inner sheath 430 may be advanced and retracted relative toouter sheath 420 by the clinician during the implantation procedure, ifdesired, as inner sheath 430 is slidable within inner lumen 424 of outersheath 420. For example, inflatable member 432 may be remotely deflatedby the clinician. Once inflatable member 432 is deflated, the clinicianmay pull into inflatable member 432 into inner lumen 424 of outer sheath420 by pulling on the proximal end of inner sheath 430.

After the assembly of outer sheath 420 and inner sheath 430 is advancedalong guidewire 410 until distal opening 422 of outer sheath 420 isproximate the target site within the patient (FIG. 11B), the clinicianremotely deflates inflatable member 432 retracts inner sheath 430 andguidewire 410 into distal opening 422 of outer sheath 420 (FIG. 11C).Then guidewire 410 and inner sheath 430 are withdrawn from outer sheath420 (FIG. 11D). For example, a clinician may simply pull on guidewire410 and inner sheath 430 from a proximal end of outer sheath 420 toslide guidewire 410 and inner sheath 430 out of the proximal opening ofouter sheath 420.

Inflatable member 432 serves to improve deliverability by protecting thedistal edge of outer sheath 420. In addition, inflatable member 432 mayenhance trackability by providing a distal force input on the assemblyof outer sheath 420 and inner sheath 430. For example, inflatable member432 can be inflated in the blood stream to allow blood flow to carry theassembly of outer sheath 420 and inner sheath 430 through the patientanatomy and ultimately to the target implant site. In addition, vesselsizing can be done by occluding a vasculature proximate to the targetsite and applying a localized contrast injection in combination withfluoroscopy.

FIGS. 12A-12C illustrate example techniques for intravascular deliveryof IMD 380 using delivery catheter 400. Delivery catheter 400 includeselongated outer sheath 460, which forms inner lumen 464 with distalopening 462. Delivery catheter 400 further includes inner sheath 440with inflatable member 432 at its distal end. Delivery catheter 400 andouter sheath 460 is sized to traverse a vasculature of the patient, anddelivery catheter 400 is configured to carry IMD 380 within a distalportion of inner lumen 464 of outer sheath 460 while traversing thevasculature of the patient. Inner sheath 440 is slidable within innerlumen 464 of outer sheath 460.

Inflatable member 432 may be constructed of a compliant polymer materialor be constructed of less-compliant polymers, if so desired. The polymermaterial may have a low-pressure rating, as high-pressure capability isnot required. The diameter of inflatable member 432 may controlled byinflation media volume. For example, inner sheath 440 may include aninflation lumen extending a length of inner sheath 440. The distal endof the inflation lumen terminates at inflatable member 432, whereas theproximal end of the inflation lumen terminates at an inflation controlmechanism, like a syringe. The inflation media is normally, but notnecessarily, a liquid, such as a saline solution; in other examples theinflation media may be a gas, such as air.

IMD 380 includes expandable fixation element 381, which is deployablefrom a collapsed position to an expanded position secure the IMD 380proximate a target site within a patient. While FIGS. 12A-12C illustrateimplantation techniques using IMD 380, in different examples, IMD 380may be substantially similar to IMD 17 (FIG. 4) or IMD 15 (FIG. 5). Asone example, the techniques of FIGS. 12A-12C may be used to deliver IMD17 to a position within a heart of a patient, such as a positionproximate to an inner wall of the right ventricle, within the rightatrium, the left atrium, and/or left ventricle. As another example, thetechniques of FIGS. 12A-12C may be used to deliver IMD 15 to anintravascular position such as a pulmonary artery or other vasculatureof the patient.

During an implantation procedure, a clinician first positions deliverycatheter 400 such that the distal end of outer sheath 460 is proximateto a target site within the patient via a vasculature accessed during asurgical procedure, as represented by FIG. 12A. For example, deliverycatheter 400 may be advanced into an entry vessel, such as the femoralartery, and then manipulated and navigated through the patient'svasculature until the distal end of outer sheath 460 proximate to atarget site within the patient. In different examples, delivery catheter400 may be steerable or be configured to traverse a guidewire to bedirected to the target site from the access point of the vasculature.The clinician may use imaging techniques, such as fluoroscopy, tomonitor the position of outer sheath 460, inner sheath 440, and IMD 380throughout the implantation procedure. In some examples, deliverycatheter 400 may have an internal lumen for contrast injections.

Delivery catheter 400 further includes stopper 441, which is proximallylocated relative to inflatable member 432. Inflatable member 432 isremotely controllable from a proximal end of delivery catheter 400 toretract in a proximal direction towards inner sheath 440. Once thedistal end of outer sheath 460 is proximate to a target site within thepatient, the clinician may deflate inflatable member 432 and drawinflatable member 432 back towards stopper 441 prior to deployment ofIMD 380. As represented by FIG. 12B, inflatable member 432 isretractable to a position within inner lumen 464 of outer sheath 460that is proximal to IMD 380. Retracting inflatable member 432 to aposition that is proximal to IMD 380 prior to deployment of IMD 380prevents the opportunity for post-deployment interaction betweeninflatable member 432 and IMD 380. For example, if inflatable member 432were not refracted to a position that is proximal to IMD 380 prior todeployment of IMD 380, inflatable member might catch on IMD 380 afterIMD 380 were deployed, which could move or even dislodge IMD 380 fromthe target site within the patient.

Stopper 441 includes an enlarged distal end that facilitates deploymentof IMD 380 out of distal opening 462 of outer sheath 460. Enlargeddistal end 441 may include a recess to receive a deflated inflatablemember 432. In any event, inner sheath 440 is remotely controllable froma proximal end of inner sheath 430 to release IMD 380 from the distalend of outer sheath 460. Once inflatable member 432 retracted to aposition within inner lumen 464 of outer sheath 460 that is proximal toIMD 380, the clinician deploys IMD 380 from outer sheath 460.Specifically, a clinician, from the proximal end of inner sheath 440,may remotely move inner sheath 440 distally relative to deployment bay442 to push IMD 380 out distal opening 462 of outer sheath 460. As shownin FIG. 12C, expandable fixation element 381 of IMD 380 is expanded froma collapsed position to an expanded position as IMD 380 passes outdistal opening 462 of outer sheath 460. In one example, inner sheath 440is held in a fixed location while outer sheath 460 is retractedproximally to release IMD 380 from distal opening 462 and allow theexpansion of IMD 380 at the target location. In the expanded position,expandable fixation element 381 will secure IMD 380 within the patient,e.g., as described with respect to IMD 17 (FIG. 4) or IMD 15 (FIG. 5).

Delivery catheter 400 may provide one or more advantages. For example,inflatable member 432 may provide improved deliverability of deliverycatheter 400 in the inflated state in that inflatable member 432 maycross tricuspid and pulmonary valves without issue or risk of damagingleaflets, e.g., to reach a target site within a pulmonary artery.Inflatable member 432 may also allow delivery catheter 400 to negotiatethe chordae in the right ventricle without hanging up on the chordae.Furthermore, inflatable member 432 may be used to measure the size of avasculature, which may be useful to find a target site having a vesselsize corresponding to the size of expandable fixation element 381. Asone example, a clinician may find a target site by applying a localizedcontrast injection while viewing delivery catheter 400 underfluoroscopy. Once a vasculature is fully occluded by inflatable member432, the clinician would then know the size of the vasculaturecorresponds to the diameter of inflatable member 432. In some examples,the clinician may selectively inflatable member 432 to a size associatedwith a desired size of the vasculature and advance delivery catheter 400within the vessel until a vasculature is fully occluded.

Inflatable member 432 is shown in further detail in FIGS. 13A-13B.Specifically, FIG. 13A is a cross-sectional illustration of inflatablemember 432 in a deflated configuration, whereas FIG. 13B is across-sectional illustration of inflatable member 432 in an inflatedconfiguration.

As shown in FIGS. 13A-13B, inner sheath 430 includes two coaxial lumens.Tube 452 provides central lumen 434 may serve as a guidewire lumen, andmay also be suitable for contrast injections. Tube 450 surrounds tube452 and provides annular inflation lumen 433. The distal end of annularinflation lumen 433 terminates at inflatable member 432, whereas theproximal end of annular inflation lumen 433 terminates at an inflationcontrol mechanism, like a syringe. Inflatable member 432 is secured tothe outside of tube 450 at the distal end of tube 450. Tube 450 includesapertures 435, which allow the inflation media to pass from withininflation lumen 433 to inflatable member 432. In other examples, tube450 may include a single aperture in place of apertures 435. The areabetween the distal ends of tubes 450, 452 is sealed to direct theinflation media inflatable member 432. As mentioned previously, theinflation media is normally, but not necessarily, a liquid, such as asaline solution.

FIG. 14 illustrates the distal end of inner sheath 470, which providesan alternative design as compared to inner sheath 430. Specifically,inner sheath 470 includes tapered flexible tip 480, which is locateddistally relative to inflatable member 432. Tapered flexible tip 480 ismounted to the distal end of tube 452, distally relative to inflatablemember 432. Central lumen 434 extends through tube 452 and throughtapered flexible tip 480. The other components and features of thedistal end of inner sheath 470 are substantially similar to those ofinner sheath 430. For brevity, these components and features are notdiscussed with respect to inner sheath 470.

Tapered flexible tip 480 is formed from a compliant biocompatiblematerial, such as silicon. Tapered flexible tip 480 may serve to help adelivery catheter, such as delivery catheter 400, navigate a guidewireto negotiate the vasculature of a patient. For example, tapered flexibletip 480 may lead inflatable member 432 around bends, vascular branchesand through valves such as tricuspid and pulmonary valves, the chordaein the right ventricle and other obstacles during positioning of adelivery catheter. Thus, tapered flexible tip 480 may improve thedeliverability of delivery catheter by preventing hang-ups duringinsertion of the delivery catheter. In some examples, the material oftapered flexible tip 480 may be doped with radiopaque materials (such asbarium sulfate) to aid a clinician during implant.

FIGS. 15A-15F illustrate exemplary techniques for intravascular deliveryof IMD 380 using delivery catheter 500. Delivery catheter 500 includeselongated outer sheath 520 and elongated inner sheath 540. Deliverycatheter 500 and outer sheath 520 are sized to traverse a vasculature ofthe patient, and delivery catheter 500 is configured to carry IMD 380within a distal portion of inner lumen 524 of outer sheath 520 whiletraversing the vasculature of the patient. Inner sheath 540 is slidablewithin outer sheath 520 and includes enlarged distal portion 532 andtether 550. Enlarged distal portion 532 provides a tapered distal end.Alternatively, an enlarged distal portion may be selected from theexamples shown previously with respect to FIGS. 13-14. In some examples,inner sheath 540 and enlarged distal portion 532 may include a lumen(not shown) configured to receive a guidewire and/or deliver contrastinjections during an implantation procedure.

IMD 380 includes expandable fixation element 381, which is deployablefrom a collapsed position to an expanded position secure the IMD 380proximate a target site within a patient. While FIGS. 15A-15F illustrateimplantation techniques using IMD 380, in different examples, IMD 380may be substantially similar to IMD 17 (FIG. 5) or IMD 15 (FIG. 5). Asone example, the techniques of FIGS. 15A-15F may be used to deliver IMD17 to a position within a heart of a patient, such as a positionproximate to an inner wall of the right ventricle, within the rightatrium, the left atrium, and/or left ventricle. As another example, thetechniques of FIGS. 15A-15F may be used to deliver IMD 15 to anintravascular position such as a pulmonary artery or other vasculatureof the patient.

During an implantation procedure, a clinician first positions deliverycatheter 500 such that the distal end of outer sheath 520 is proximateto a target site within the patient via a vasculature accessed during asurgical procedure, as represented by FIG. 15A. For example, deliverycatheter 500 may be advanced into an entry vessel, such as the femoralartery, and then manipulated and navigated through the patient'svasculature until the distal end of outer sheath 520 proximate to atarget site within the patient. In different examples, delivery catheter500 may be steerable or be configured to traverse a guidewire to bedirected to the target site from the access point of the vasculature.The clinician may use imaging techniques, such as fluoroscopy, tomonitor the position of outer sheath 520, inner sheath 540, and IMD 380throughout the implantation procedure. In some examples, deliverycatheter 500 may have an internal lumen for contrast injections.

Enlarged distal portion 532 is configured to substantially fill innerlumen 524 of outer sheath 520 and close-off distal opening 522 of outersheath 520 while delivery catheter 500 is advanced to a locationproximate a target site within a patient. As one example, enlargeddistal portion 532 may provide a tapered distal end with a profilelarger than a cross section of inner lumen 524 of outer sheath 520 suchthat the tapered distal end cannot pass through inner lumen 524.

After positioning the distal end of outer sheath 520 is proximate to atarget site within the patient, the clinician moves enlarged distalportion 532 distally relative to distal opening 522 of outer sheath 520to allow room for IMD 380 to deploy from distal opening 522 of outersheath 520 (FIG. 15B). In some examples, the clinician may retractsheath 520 proximally to expose and allow fixation of IMD 380 to seat ina vessel wall. Thereafter, tip 532 is retracted while helix 552 insuresthat IMD 380 is not dislodged from the vessel wall while tip 532 isretracted past the implant.

Inner sheath 540 facilitates deployment of IMD 380 out of distal opening522 of outer sheath 520. In particular, inner sheath 540 includes tether550, which has helical element 552 on its distal end. Tether 550 isremotely controllable from a proximal end of inner sheath 540 to releaseIMD 380 from the distal end of outer sheath 520. Specifically, aclinician, from the proximal end of inner sheath 540, may remotely pushtether 550 distally relative to the distal end of outer sheath 520 topush IMD 380 out distal opening 522 of outer sheath 520, e.g., byholding tether 550 in place and retracting outer sheath 520 (FIG. 15C).As shown in FIG. 15C, a portion of expandable fixation element 381 ofIMD 380 is expanded from a collapsed position to an expanded position asIMD 380 passes out of distal opening 522 of the distal end of outersheath 520. In the expanded position, expandable fixation element 381will secure IMD 380 within the patient, e.g., as described with respectto IMD 17 (FIG. 4) or IMD 15 (FIG. 5).

Then the clinician may, again from the proximal end of inner sheath 540,move enlarged distal portion 532 proximally towards distal opening 522of outer sheath 520, past IMD 380 and helical element 552 while helicalelement 552 remains engaged to the looped fixation element of IMD 380(FIG. 15D). In this manner, IMD 380 is not fully deployed when enlargeddistal portion 532 is retracted past IMD 380. Once the clinicianretracts enlarged distal portion 532 proximally past IMD 380 and helicalelement 552, the clinician may, again from the proximal end of innersheath 540, remotely rotate tether 550 such that helical element 552releases a looped element of IMD 380 to deploy IMD 380 (FIG. 15E).Specifically, in the example illustrated in FIG. 15E, expandablefixation element 381 is the looped element of IMD 380, and rotatinghelical element 552 releases expandable fixation element 381 from innersheath 540.

At this point, IMD 380 is fully deployed proximate to the target site,e.g., within a vasculature of the patient. However, the clinician mayoptionally recapture IMD 380 by first grabbing a looped element of IMD380, e.g., expandable fixation element 381, with helical element 552,and then using tether 550 to pull IMD 380 into the distal end of outersheath 520. In this manner, tether 550 may be used to adjust theposition of IMD 380 after full deployment, or to remove IMD 380 from thepatient after full deployment. As one example, the clinician may decideto remove IMD 380 from the patient after full deployment if electronictesting of IMD 380 produces unsatisfactory results. As another example,the clinician may decide to remove IMD 380 from the patient after fulldeployment if the clinician determines that expandable fixation element381 is improperly sized to locate IMD 380 at the target site. In such anexample, IMD 380 may be replaced with an IMD including an expandablefixation element with a proper size. As another example, a clinician mayuse delivery catheter 500 to remove IMD 380 during a subsequent surgicalprocedure, e.g., once IMD 380 has met or exceeded its projectedlifespan. During such a subsequent surgical procedure, IMD 380 could bereplaced with a new IMD using the same outer sheath used during theremoval of IMD 380.

After IMD 380 is fully deployed proximate to the target site, theclinician retracts tether 550 and enlarged distal portion 532 into innerlumen 524 of outer sheath 520 and withdraws delivery catheter 500 (FIG.15F).

FIGS. 16A-16B illustrate example techniques for intravascular deliveryof IMD 380 using delivery catheter 560. Delivery catheter 560 includeselongated outer sheath 520 and elongated inner sheath 570. Deliverycatheter 560 and outer sheath 520 are sized to traverse a vasculature ofthe patient, and delivery catheter 560 is configured to carry IMD 380within a distal portion of inner lumen 524 of outer sheath 520 whiletraversing the vasculature of the patient. Inner sheath 570 is slidablewithin outer sheath 520 and includes enlarged distal portion 562 andtether 552.

Delivery catheter 560 is substantially similar to delivery catheter 500,except that enlarged distal portion 562 includes an inflatable member.In some examples, inner sheath 570 and enlarged distal portion 562 mayinclude a lumen (not shown) configured to receive a guidewire and/ordeliver contrast injections during an implantation procedure. Forexample, the inflatable member of enlarged distal portion 562 may befunctionally similar to inflatable member 432 (FIGS. 13A-13B) and mayoptionally include a tapered flexible tip, such as tapered flexible tip480 (FIG. 14). The other components and features of delivery catheter560 are substantially similar to those of delivery catheter 500. Forbrevity, these components and features are discussed in limited detailwith respect to delivery catheter 560.

During an implantation procedure, a clinician first positions deliverycatheter 560 such that the distal end of outer sheath 520 is proximateto a target site within the patient via a vasculature accessed during asurgical procedure, as represented by FIG. 16A. For example, deliverycatheter 560 may be advanced into an entry vessel, such as the femoralartery, and then manipulated and navigated through the patient'svasculature until the distal end of outer sheath 520 proximate to atarget site within the patient. In different examples, delivery catheter560 may be steerable or be configured to traverse a guidewire to bedirected to the target site from the access point of the vasculature.The clinician may use imaging techniques, such as fluoroscopy, tomonitor the position of outer sheath 520, inner sheath 570, and IMD 380throughout the implantation procedure.

Enlarged distal portion 562 is configured to substantially fill innerlumen 524 of outer sheath 520 and close-off distal opening 522 of outersheath 520 while the inflatable member of enlarged distal portion 562 isinflated. The inflatable member of enlarged distal portion 562 isgenerally inflated while delivery catheter 560 is advanced to a locationproximate a target site within a patient. After positioning the distalend of outer sheath 520 is proximate to a target site within thepatient, the clinician deflates the inflatable member of enlarged distalportion 562 and retracts enlarged distal portion 562 proximally intoinner lumen 524 of outer sheath 520 to a position that is proximal toIMD 380 within inner lumen 524 of outer sheath 520.

Inner sheath 570 facilitates deployment of IMD 380 out of distal opening522 of outer sheath 520. In particular, inner sheath 570 includes tether550, which has helical element 552 on its distal end. Tether 550 isremotely controllable from a proximal end of inner sheath 570 to releaseIMD 380 from the distal end of outer sheath 520. Specifically, aclinician, from the proximal end of inner sheath 570, may remotely pushtether 550 distally relative to the distal end of outer sheath 520 topush IMD 380 out distal opening 522 of outer sheath 520 (FIG. 16B). Asshown in FIG. 16B, expandable fixation element 381 of IMD 380 isexpanded from a collapsed position to an expanded position as IMD 380passes out of distal opening 522 of the distal end of outer sheath 520.In the expanded position, expandable fixation element 381 will secureIMD 380 within the patient, e.g., as described with respect to IMD 17(FIG. 4) or IMD 15 (FIG. 5).

Once the clinician retracts enlarged distal portion 562 proximally pastIMD 380 and helical element 552, the clinician may, again from theproximal end of inner sheath 570, remotely rotate tether 550 such thathelical element 552 releases a looped element of IMD 380 to deploy IMD380.

At this point, IMD 380 is fully deployed proximate to the target site,e.g., within a vasculature of the patient. However, the clinician mayoptionally recapture IMD 380 by first grabbing a looped element of IMD380, e.g., expandable fixation element 381, with helical element 552,and then using tether 550 to pull IMD 380 into the distal end of outersheath 520. In this manner, tether 550 may be used to adjust theposition of IMD 380 after full deployment, or to remove IMD 380 from thepatient after full deployment.

FIGS. 17A-17E illustrate exemplary techniques for intravascular deliveryof IMD 380 with a kit including outer sheath 620 and inner sheath 640.Inner sheath 640 is configured to carry IMD 380 at its distal end. Innersheath 640 forms a slit at its distal end to facilitate deployment ofIMD 380. Specifically, FIGS. 17A-17E illustrate distal portions of outersheath 620 and elongated inner sheath 640. In some examples, outersheath 620 may be considered to be substantially similar to outer sheath234. For example, outer sheath 620 may be included in an assembly withcoupling module 206. In such an example, inner sheath 640 may beslidably coupled to coupling module 226 in a mating assembly, and thedistal end of inner sheath 640 may be positioned proximate a target sitewithin a patient in a similar manner that inner sheath 202 is positionedproximate a target site within a patient as described with respect toFIGS. 8A-8E.

While FIGS. 17A-17E illustrate implantation techniques using IMD 380, indifferent examples, IMD 380 may be substantially similar to IMD 17 (FIG.4) or IMD 15 (FIG. 5). As one example, the techniques of FIGS. 17A-17Emay be used to deliver IMD 17 to a position within a heart of a patient,such as a position proximate to an inner wall of the right ventricle,within the right atrium, the left atrium, and/or left ventricle. Asanother example, the techniques of FIGS. 17A-17E may be used to deliverIMD 15 to an intravascular position such as a pulmonary artery or othervasculature of the patient.

The distal end of inner sheath 640 is configured to carry IMD 380through inner lumen 624 of outer sheath 620, and inner sheath 640 isslidable within inner lumen 624 of outer sheath 620. Inner sheath 640facilitates deployment of IMD 380 out of distal opening 622 of outersheath 620. In particular, inner sheath 640 forms slit 641, which allowsinner sheath 640 to uncurl to expose the IMD 380 when the distal end ofinner sheath 640 passes out of distal opening 622 of outer sheath 620.The distal end of inner sheath 640 is elastically deformed within innerlumen 624 such that the distal end of inner sheath 640 is biased touncurl and expose IMD 380 when the distal end of inner sheath 640 passesout of distal opening 622 of outer sheath 620.

During an implantation procedure, a clinician may first position outersheath 620 such that distal opening 622 of outer sheath 620 is proximateto a target site within the patient via a vasculature accessed during asurgical procedure, as represented by FIG. 17A. For example, outersheath 620 may be advanced into an entry vessel, such as the femoralvein and then manipulated and navigated through the patient'svasculature distal opening 622 of outer sheath 620 is proximate to atarget site within the patient. In different examples, outer sheath 620may be steerable or be configured to traverse a guidewire to be directedto the target site from the access point of the vasculature. Theclinician may use imaging techniques, such as fluoroscopy, to monitorthe position of outer sheath 620, inner sheath 640, and IMD 380throughout the implantation procedure.

After locating distal opening 622 of outer sheath 620 proximate to atarget site within the patient, the clinician may remotely push innersheath 640 distally relative to outer sheath 620 to expose the distalend of inner sheath 640 and IMD 380, e.g., by holding inner sheath 640in place and retracting outer sheath 620. IMD 380 includes expandablefixation element 381, which is deployable from a collapsed position toan expanded position secure the IMD 380 proximate a target site within apatient. When exposed, a portion of expandable fixation element 381 mayassume the expanded position, as shown in FIG. 17B.

As shown in FIG. 17B, IMD 380 is partially deployed from inner sheath640. Only a portion of expandable fixation element 381 has assumed theexpanded position. At this point, the clinician may retract the distalend of inner sheath 640 into inner lumen 624 of outer sheath 620 toreturn the IMD 380 to inner lumen 624 of outer sheath 620. When thedistal end of inner sheath 640 and IMD 380 are returned to inner lumen624 of outer sheath 620, the distal end of inner sheath 640 curls andthe expanded portion of expandable fixation element 381 resumescollapsed position to fit within inner lumen 624 of outer sheath 620.

As one example, the clinician may partially deploy IMD 380 and performelectronic testing of IMD 380, as sensing elements of IMD 380, such as apressure sensor, may be exposed when IMD 380 is partially deployed. Theclinician may decide to remove IMD 380 from the patient after partialdeployment if testing results are unsatisfactory or if the cliniciandetermines that expandable fixation element 381 is improperly sized tolocate IMD 380 at the target site. In such an example, IMD 380 may bereplaced with an IMD including an expandable fixation element with aproper size.

As represented by FIG. 17C, once IMD 380 is fully exposed, at least aportion of expandable fixation element 381 of IMD 380 has assumed theexpanded position. In order to fully deploy IMD 380 from inner sheath640, the clinician then retracts inner sheath 640 into inner lumen 624of outer sheath 620 after the portion of expandable fixation element 381assumes the expanded position (FIG. 17D). This causes the distal end ofouter sheath 620 to interact with expandable fixation element 381 toslide IMD 380 out of inner lumen 624 of outer sheath 620 (FIG. 17E). Inan example, the clinician may hold inner sheath 640 in place whileadvancing outer sheath 620 to cause the distal end of outer sheath 620to interact with expandable fixation element 381 to slide IMD 380 out ofinner lumen 624 of outer sheath 620.

FIGS. 18A-18C illustrate techniques for measuring the size ofvasculature 700 using deployment receptacle 340 of FIGS. 10A-10D withIMD 380 partially deployed from deployment receptacle 340. As shown inFIG. 18A, the distal end of deployment receptacle 340, which includesdeployment bay 342, is delivered adjacent a target site withinvasculature 700 through outer sheath 320. As one example, vasculature700 may be a pulmonary artery or other vasculature of the patient.

Tether 350 with helical element 352 is then used to partially deploy IMD380 from distal opening 322 of outer sheath 320. As shown in FIG. 18B, aportion of expandable fixation element 381 assumes the expanded positionwhen IMD 380 is partially deployed from the distal opening.

Outer sheath 320, deployment receptacle 340 and the partially deployedIMD 380 is then advanced within the vasculature (FIG. 18C). A clinicianmonitors the process of outer sheath 320, deployment receptacle 340 andthe partially deployed IMD 380. Specifically, the clinician monitorsvasculature 700 and/or the expanded portion of expandable fixationelement 381 for deflection to determine when the size of the expandedportion of expandable fixation element 381 corresponds to the size ofvasculature 700. For example, vasculature 700 may be tapered, and IMD380 may be configured to best fit when the size of the expanded portionof expandable fixation element 381 corresponds to the size ofvasculature 700. In this manner, the expanded portion of expandablefixation element 381 may be used to measure the size of vasculature 700to determine a target side for deployment of IMD 380 within vasculature700. Deflection by either vasculature 700 or the expanded portion ofexpandable fixation element 381 may indicate the size of the expandedportion of expandable fixation element 381 corresponds to the size ofvasculature 700.

In an example, the clinician may use fluoroscopy to view vasculature 700and/or the expanded portion of expandable fixation element 381 whileadvancing outer sheath 320, deployment receptacle 340 and the partiallydeployed IMD 380 within vasculature 700. The clinician may also inject acontrast dye within vasculature 700 to aid in the monitoring of theexpanded portion of expandable fixation element 381 and vasculature 700.

Once the clinician determines when the size of the expanded portion ofexpandable fixation element 381 corresponds to the size of vasculature700, the clinician may deploy IMD 380 within vasculature 700 inaccordance with the techniques described with respect to FIGS. 10A-10D.

FIG. 19 illustrates techniques for measuring the size of vasculature 700using outer sheath 620 and inner sheath 640 of FIGS. 17A-17E with IMD380 partially deployed from inner sheath 640. The distal end of innersheath 640 is delivered adjacent a target site within vasculature 700through outer sheath 320. As one example, vasculature 700 may be apulmonary artery or other vasculature of the patient.

Inner sheath 640 is then used to partially deploy IMD 380 from distalopening 622 of outer sheath 620. As shown in FIG. 19, a portion ofexpandable fixation element 381 assumes the expanded position when IMD380 is partially deployed from distal opening 622 of outer sheath 620.

Outer sheath 620, inner sheath 640 and the partially deployed IMD 380 isthen advanced within the vasculature. A clinician monitors the processof outer sheath 620, inner sheath 640 and the partially deployed IMD380. Specifically, the clinician monitors vasculature 700 and/or theexpanded portion of expandable fixation element 381 for deflection todetermine when the size of the expanded portion of expandable fixationelement 381 corresponds to the size of vasculature 700. For example,vasculature 700 may be tapered, and IMD 380 may be configured to bestfit when the size of the expanded portion of expandable fixation element381 corresponds to the size of vasculature 700. In this manner, theexpanded portion of expandable fixation element 381 may be used tomeasure the size of vasculature 700 to determine a target side fordeployment of IMD 380 within vasculature 700. Deflection by eithervasculature 700 or the expanded portion of expandable fixation element381 may indicate the size of the expanded portion of expandable fixationelement 381 corresponds to the size of vasculature 700.

In an example, the clinician may use fluoroscopy to view vasculature 700and/or the expanded portion of expandable fixation element 381 whileadvancing outer sheath 620, inner sheath 640 and the partially deployedIMD 380 within vasculature 700. The clinician may also inject a contrastdye within vasculature 700 to aid in the monitoring of the expandedportion of expandable fixation element 381 and vasculature 700.

Once the clinician determine when the size of the expanded portion ofexpandable fixation element 381 corresponds to the size of vasculature700, the clinician may deploy IMD 380 within vasculature 700 inaccordance with the techniques described with respect to FIGS. 17A-17E.

FIG. 20 illustrates techniques for measuring the size of vasculature 700using delivery catheter 500 of FIGS. 16A-16B. As described previously,delivery catheter 500 includes inner sheath 540 with inflatable distalportion 562. As shown in FIG. 20, the distal end of outer sheath 520 isdelivered adjacent a target site within vasculature 700. As one example,vasculature 700 may be a pulmonary artery or other vasculature of thepatient.

Inflatable distal portion 562 may be inflated during the insertion ofdelivery catheter 500 as described with respect to FIGS. 16A-16B.Inflatable distal portion 562 may be used to measure the size ofvasculature 700. For example, a clinician may monitor vasculature 700during the insertion of delivery catheter 500; once vasculature 700 isoccluded by inflatable distal portion 562, the clinician will know thatthe size of vasculature 700 at that location corresponds to the inflatedsize of inflatable distal portion 562. In some examples, the clinicianmay adjust the inflated size of inflatable distal portion 562 to measurethe size of vasculature 700. In other examples, the clinician maymaintain the inflated size of inflatable distal portion 562 to find thelocation within vasculature 700 that corresponds to the inflated size ofinflatable distal portion 562. In any event, once the clinician hasfound a suitable target site within vasculature 700, the clinician maydeploy IMD 380 from delivery catheter 500 in accordance with thetechniques described with respect to FIGS. 16A-16B.

FIG. 21 is a flowchart illustrating techniques for measuring the size ofa vasculature using a partially deployed IMD. For example, thetechniques of FIG. 21 may be performed using deployment receptacle 340of FIGS. 10A-10D or using outer sheath 620 and inner sheath 640 of FIGS.17A-17E. In a further example, the techniques of FIG. 21 may beperformed using the system for intravascular delivery of an IMDdescribed with respect to FIGS. 6-8E.

First, a distal end of an elongated outer sheath forming an inner lumenwith a distal opening is positioned adjacent a target site within avasculature of a patient (702). Then an IMD is partially deployed fromthe distal opening of the outer sheath (704). The IMD includes anexpandable fixation element expandable from a collapsed position to anexpanded position, and at least a portion of the expandable fixationelement assumes the expanded position when the implantable medicaldevice is partially deployed from the distal opening.

After the IMD is partially deployed from the distal opening of the outersheath, the distal end of the outer sheath with the implantable medicaldevice partially deployed from the distal opening is advanced within thevasculature (706). While advancing the distal end of the outer sheathwith the implantable medical device partially deployed from the distalopening, at least one of the vasculature and the portion of theexpandable fixation element is monitored for deflection to determinewhen the size of the portion of the expandable fixation elementcorresponds to the size of the vasculature (708). Monitoring at leastone of the vasculature and the portion of the expandable fixationelement for deflection may include using fluoroscopy to view at leastone of the vasculature and the portion of the expandable fixationelement while advancing the distal end of the outer sheath within thevasculature. In addition, monitoring at least one of the vasculature andthe portion of the expandable fixation element for deflection may alsoinclude injecting a contrast dye within the vasculature.

After determining the size of the portion of the expandable fixationelement corresponds to the size of the vasculature, the techniques mayinclude fully releasing the implantable medical device to deploy theimplantable medical device within the vasculature (710).

In examples in which the IMD includes a pressure sensor, the techniquesmay further include monitoring pressure within the vasculature with thepressure sensor with the implantable medical device partially deployedfrom the distal opening to test the functionality of IMD at thatlocation, and after verifying the functionality of implantable medicaldevice at that location, fully releasing the implantable medical deviceto deploy the implantable medical device within the vasculature. Forexample, such a testing may include receiving an indication of themonitored pressure from the IMD with an external programmer, such asprogrammer 24 (FIG. 1).

FIGS. 22-24C illustrate example techniques for intravascular delivery ofIMD 380 using delivery catheter 800. Delivery catheter 800 includestether 850, which forms loop 851 to engage a looped element of the IMD380, such as an expandable fixation element of IMD 380. FIG. 22illustrates a portion of delivery catheter 800 near the distal end ofdelivery catheter 800 whereas FIGS. 23A-23D illustrate deployment of IMD380 from the distal end of delivery catheter 800. FIGS. 24A-24Cillustrate deployment handle 860 at the proximal end of deliverycatheter 800. Deployment handle 860 may be operated by a clinicianduring an implantation procedure to remotely deploy IMD 380 from thedistal end of delivery catheter 800 as shown in FIGS. 23A-23D. Inparticular, deployment handle 860 may be used to retract outer sheath820 to expose IMD 380 while inner sheath 830 holds IMD 380 at a targetlocation within the patient.

As shown in FIG. 22, delivery catheter 800 includes elongated outersheath 820 forming inner lumen 821 with distal opening 822. Outer sheath820 is sized to traverse a vasculature of the patient. Delivery catheter800 further includes elongated inner sheath 830. Elongated inner sheath830 includes stopper 840, which is configured to engage a proximal sideof IMD 380 to preclude IMD 380 from being located at a more proximalposition than stopper 840 within inner lumen 821 of outer sheath 820. Inone example, stopper 840 may substantially fill inner lumen 821 of outersheath 820. In different examples, distal side 842 of stopper 840 mayhave a concave shape or be substantially flat.

Inner sheath 830 further includes tether 850, which is configured toform loop 851 on distal side 842 of stopper 840. Loop 851 is configuredto engage a looped element of IMD 380 (not shown in FIG. 22) to coupleIMD 380 to inner sheath 830. In different examples, tether 850 may beformed from a suture-like thread material or from a shape memory alloysuch as Nitinol.

As described in further detail with respect to FIGS. 23A-24C, innersheath 830 and stopper 840 are slidable relative to outer sheath 820. Inparticular, stopper 840 is slidable between a position that isproximally located relative to distal opening 822 of outer sheath 820and a position in which at least a portion of stopper 840 is distallylocated relative to distal opening 822 of outer sheath 820. In oneexample, while positioning the distal end of catheter 800 proximate atarget site within a vasculature of a patient during an implantationprocedure, stopper 840 may be located entirely within inner lumen 821 ofouter sheath 820 such that IMD 380 fits within inner lumen 821 of outersheath 820 at a position distal to the position of stopper 840 withininner lumen 821 of outer sheath 820. Further, tether 850 forms loop 851on distal side 842 of stopper 840. Loop 851 engages a looped element ofIMD 380 (not shown in FIG. 22) to couple IMD 380 to inner sheath 830during the positioning of the distal end of catheter 800 proximate thetarget site within the vasculature of the patient during theimplantation procedure.

During the implantation procedure, one the distal end of catheter 800 ispositioned proximate the target site within the vasculature of thepatient, the clinician may partially retract outer sheath 820 to exposeIMD 380, but tether remains engaged with the looped element of IMD 380.If the clinician is satisfied with the position of IMD 380, theclinician may then further retract outer sheath 820 such that at least aportion of stopper 840 is distally located relative to distal opening822 of outer sheath 820. When stopper is located in this position,tether 850 releases the looped element of IMD 380.

Specifically, one end of tether 850 is fixed to stopper 840 and thesecond end of tether 850 includes bead 852. When tether 850 forms theloop, bead 852 is located within inner lumen 821 of outer sheath 820proximal to stopper 840. In this position, bead 852 is pinched betweenan inner surface of outer sheath 820 and a proximal side of stopper 840.Retracting outer sheath 820 such that at least a portion of stopper 840is distally located relative to distal opening 822 of outer sheath 820serves to free bead 852 from between an inner surface of outer sheath820 and the proximal tapered surface of stopper 840 to open lopped 851.

In the example shown in FIG. 22, the proximal side of stopper 840 istapered from an inner diameter to an outer diameter of stopper 840. Bead852 provides a tapered profile configured to register with the taper ofthe proximal side of stopper 840 and the inner surface of the outersheath 820. The tapered profile of bead 852 may mitigate binding betweenouter sheath 820, bead 852 and stopper 840 as compared to a bead havinga different shape, such as a sphere shape. As also shown in the exampleshown in FIG. 22, stopper 840 includes groove 849 adjacent to outersheath 820. Groove 849 is configured to receive tether 850 when tether850 forms loop 851. This may further mitigate binding, i.e., bindingbetween outer sheath 820, tether 850 and stopper 840.

As shown in FIG. 22, inner sheath 830 includes inner shaft 831, whichextends from a proximal end of inner sheath 830 to a distal end of innersheath 830 including through stopper 840. Inner sheath 830 furtherincludes outer shaft 832 that extends from the proximal end of innersheath 830 to a position within stopper 840 such that a distal end ofouter shaft 832 is within stopper 840. In an example, outer shaft 832 isshrink tubing formed over inner sheath 830. In one example, stopper 840is an overmold that encapsulates the distal end of outer shaft 832 and aportion of inner shaft 831 to fix the position of outer shaft 832relative to inner shaft 831.

Outer shaft 832 provides stiffness to inner sheath 830 between theproximal end of inner sheath 830 and stopper 840. The stiffness providedby shaft 832 may mitigate buckling of inner sheath 830 during animplantation procedure. Meanwhile the configuration of inner sheath 830provides a smaller diameter distal to stopper 840, which increases thespace available for IMD 380 within inner lumen 821 of outer sheath 820,and reduces the outer diameter of outer sheath 820 needed for outersheath 820 to contain both inner sheath 830 and IMD 380 within thedistal portion of inner lumen 821.

As one example, the inner diameter of outer sheath 820 may be 13 French(0.13 inches) or less and the outer diameter of outer sheath 820 may beabout 3 French (0.03 inches) greater than the inner diameter of outersheath 820, i.e., 16 French or less. In some examples, the body portionof IMD 380 including a sensor may have a cross-sectional thickness ofabout 10 French (0.10 inches) and the entirety of IMD 380 includingfixation element 381 may provide a cross-sectional profile thickness ofabout 12 French (0.12 inches) when fixation element 381 is in afully-collapsed position. In an alternative configuration, a deliverycatheter similar to delivery catheter 800 may be modified to be tipless,i.e., without enlarged distal portion 835. In such a configuration,inner sheath 830 would terminate at stopper 840, and the diameter ofouter sheath 820 could be further reduced as the distal portion of innerlumen 821 would only have to be large enough to contain IMD 380 and notalso contain inner shaft 831. The dimensions provided herein are merelyexamples, and the particular sizes of the components discussed hereinmay be modified to account for different size IMDs and/or differenttarget sites and access routes within a patient.

FIGS. 23A-24C illustrate exemplary techniques for intravascular deliveryof IMD 380 using delivery catheter 800. FIGS. 23A-23D illustratedeployment of IMD 380 from the distal end of delivery catheter 800,whereas FIGS. 24A-24C illustrate deployment handle 860 at the proximalend of delivery catheter 800. Delivery catheter 800 includes elongatedouter sheath 820 and elongated inner sheath 830 in a substantiallycoaxial arrangement. Elongated outer sheath 820 and elongated innersheath 830 each extend from deployment handle 860 to the distal end ofdelivery catheter 800. Delivery catheter 800 and outer sheath 820 aresized to traverse a vasculature of the patient, and delivery catheter800 is configured to carry IMD 380 within a distal portion of innerlumen 821 of outer sheath 820 while traversing the vasculature of thepatient. Inner sheath 830 is slidable within outer sheath 820 andincludes enlarged distal portion 835 and tether 850. Enlarged distalportion 835 provides an inflatable member and flexible tapered tip 837,e.g., as described with respect to FIG. 14. In other examples, a tapereddistal end, e.g., as described with respect to FIGS. 15A-15F may be usedin place of the inflatable member. In some examples, inner sheath 830and enlarged distal portion 835 may include a lumen (not shown)configured to receive a guidewire and/or deliver contrast injectionsduring an implantation procedure.

IMD 380 includes expandable fixation element 381, which is deployablefrom a collapsed position to an expanded position secure the IMD 380proximate a target site within a patient. While FIGS. 23A-23D illustrateimplantation techniques using IMD 380, in different examples, IMD 380may be substantially similar to IMD 17 (FIG. 8) or IMD 15 (FIG. 8). Asone example, the techniques of FIGS. 23A-24C may be used to deliver IMD17 to a position within a heart of a patient, such as a positionproximate to an inner wall of the right ventricle, within the rightatrium, the left atrium, and/or left ventricle. As another example, thetechniques of FIGS. 23A-24C may be used to deliver IMD 15 to anintravascular position such as a pulmonary artery or other vasculatureof the patient.

During an implantation procedure, a clinician first positions deliverycatheter 800 such that the distal end of outer sheath 820 is proximateto a target site within the patient via a vasculature accessed during asurgical procedure, as represented by FIG. 23A. For example, deliverycatheter 800 may be advanced into an entry vessel, such as the femoralartery, and then manipulated and navigated through the patient'svasculature until the distal end of outer sheath 820 proximate to atarget site within the patient. In different examples, delivery catheter800 may be steerable or be configured to traverse a guidewire to bedirected to the target site from the access point of the vasculature.The clinician may use imaging techniques, such as fluoroscopy, tomonitor the position of outer sheath 820, inner sheath 830, and IMD 380throughout the implantation procedure. As shown in FIG. 22, outer sheath820 includes marker band 824, which is visible to the clinician duringimaging. As one example, marker band 824 may be a gold band. Bead 852and/or stopper 840 may also include radiopaque materials to aid invisibility of catheter 800 during an implantation procedure. In someexamples, bead 852 and stopper 840 may have different radiopaquematerials such that bead 852 and stopper 840 such that a clinician canclearly distinguish bead 852 and stopper 840 from one another duringimaging. In further examples, delivery catheter 800 may have an internallumen for contrast injections. As one example, the internal lumen forcontrast injections may be a guidewire lumen.

Enlarged distal portion 835 is configured to substantially fill innerlumen 821 of outer sheath 820 and close-off distal opening 822 of outersheath 820 when inflated, for example, while delivery catheter 800 isadvanced to a location proximate a target site within a patient.

After positioning the distal end of outer sheath 820 is proximate to thetarget site within the patient, the clinician operates deployment handle860 (FIGS. 24A-24C) to deploy IMD 380. As shown in FIG. 24A, deploymenthandle is located at the proximal end of outer sheath 820 and innersheath 830 (not indicated in FIG. 24A). Deployment handle 860 includessheath retraction mechanism 870, which facilitates selectivelyretracting outer sheath 820 relative to inner sheath 830 to facilitateremote deployment of IMD 380 out of the distal opening of the innerlumen of the outer sheath.

Deployment handle 860 includes body 862, which forms grip surfaces 864to improve the controllability of deployment handle 860 by a clinician.Sheath retraction mechanism 870 includes slidable deployment button 872,which is configured to selectively retract outer sheath 820 relative toinner sheath 830 when moved from a distal position on body 862 (as shownin FIG. 24A) to a more proximal position on the body (as shown in FIGS.24B and 24C). Deployment button 872 may be directly coupled to outersheath 820, whereas body 862 may be directly coupled to inner sheath 830via guidewire port 886. Body 862 includes slot 873, which allowsslidable deployment button 872 to be outside body 862 while beingconnected to outer sheath 820. Sheath retraction mechanism 870 furtherincludes positive stops 875, which individually register with deploymentbutton 872 such that a clinician can incrementally retract outer sheath820 if desired.

Deployment handle 860 further includes partial deployment lock button874. Partial deployment lock button 874 is configured to selectivelyprevent deployment button 872 from being moved to a position configuredto fully release the IMD 380 from the inner sheath, i.e., a position inwhich bead 852 is released to open loop 851.

As mentioned above, deployment handle 860 includes guidewire port 886.Inner sheath 830 includes a guidewire lumen (not shown) extendingthroughout the length of inner sheath 830, the guidewire lumen beingconfigured to slidably receive a guidewire. Guidewire port 886 is insubstantial alignment with the guidewire lumen of inner sheath 830.Guidewire port 886 facilitates removal of a guidewire from within theguidewire lumen by pulling the guidewire proximally out of guidewireport 886 and the guidewire lumen of inner sheath 830. In some examples,guidewire port 886 may include a one-way valve to prevent patient fluidsfrom flowing through guidewire lumen of inner sheath 830 and out ofguidewire port 886 once the distal end of catheter 800 is insertedwithin a patient.

Deployment handle 860 further includes flushing check valve 882.Flushing check valve 882 is a one-way valve that facilitates flushingouter sheath 820 to remove air from within outer sheath 820 prior toinserting the distal end of catheter 800 within a patient to mitigate arisk of emboli within the patient. The one-way configuration of checkvalve 882 also serves to prevent patient fluids from flowing throughinner lumen 821 of outer sheath 820 and out of check valve 882 once thedistal end of catheter 800 is inserted within a patient.

Deployment handle 860 further includes inflation port 884, which isconfigured to exchange an inflation media via inflation media tube 885.The inflation port is used to selectively inflate inflatable member 835on the distal end of inner sheath 830.

As mentioned previously, after positioning the distal end of outersheath 820 is proximate to the target site within the patient, asrepresented by FIG. 23A, the clinician evaluates inflation media frominflatable member 835 via inflation port 884 deployment handle 860, asrepresented by FIG. 23B.

Then the clinician operates deployment handle 860 to deploy IMD 380. Asshown in FIG. 24A, slidable deployment button 872 is in its most distalposition, which coincides with the distal end of outer sheath 820 beingin its most distal position as shown in FIGS. 23A and 23B. From thisposition, the clinician moves slidable deployment button 872 in aproximal direction relative to body 862 of deployment handle 860 asrepresented by FIG. 24B. This retracts outer sheath 820 relative toinner sheath 830 such that stopper 840 of pushes IMD 380 out of distalopening 822 of outer sheath 820 as represented by FIG. 23C. However,because the position of inner sheath 830 has been maintained within thepatient while outer sheath 820 is retracted, the position of IMD 380 isalso maintained within the patient while outer sheath 820 is retracted.In this manner, retracting outer sheath 820 rather than extending innersheath 830 to push IMD 380 out of distal opening 822 of outer sheath 820allows a clinician to locate IMD 380 at a target deployment site beforeIMD 380 is actually deployed.

As shown in FIG. 23C, all or a portion of expandable fixation element381 of IMD 380 is expanded from a collapsed position to an expandedposition as IMD 380 passes out of distal opening 822 of the distal endof outer sheath 820. In the expanded position, expandable fixationelement 381 will secure IMD 380 within the patient, e.g., as describedwith respect to IMD 17 (FIG. 4) or IMD 15 (FIG. 8).

Partial deployment lock button 874 of deployment handle 860 selectivelyprevents deployment button 872 from being moved to a position configuredto fully-release IMD 380 from inner sheath 830, i.e., a position inwhich bead 852 is released to open loop 851. As shown in FIG. 24B,partial deployment lock button 874 is engaged prevents slidabledeployment button 872 from moving further in a proximal direction.

If a clinician is not satisfied with the position of IMD 380 afterpartial deployment, as represented by FIG. 23C and FIG. 24B, theclinician may advance outer sheath 820 relative to inner sheath 830 bymoving deployment button 872 to its distal position as shown in FIG.24A. This relocates IMD 380 within inner lumen 821 of outer sheath 820via distal opening 822 of outer sheath 820. The clinician may thenoptionally redeploy IMD 380, e.g., at a different position within thepatient.

Once a clinician is satisfied with the position of IMD 380 after partialdeployment, as represented by FIG. 23C and FIG. 24B, the clinician mayopen partial deployment lock button 874 and move deployment button 872to a more proximal position as represented by FIG. 24C. This furtherretracts outer sheath 820 in a more proximal direction relative to innersheath 830 such that stopper 840 is positioned distally relative todistal opening 822 of outer sheath 820 to open tether loop 851 byreleasing bead 852 and release expandable fixation element 381, a loopedelement of IMD 380, from inner sheath 830 as represented by FIG. 23D tofully deploy IMD 380. Once IMD 380 is fully deployed, a clinician maywithdraw catheter 800 from the patient.

While deployment handle 860 has been described specifically with respectto catheter 800, the techniques disclosed with respect to deploymenthandle 860 may also be used with a variety of alternate catheterdesigns, including those disclosed herein.

Various examples of the disclosure have been described. These and otherexamples are within the scope of the following claims.

The invention claimed is:
 1. A kit for intravascular implantation of animplantable medical device within a patient, the kit comprising: anelongated outer sheath forming an inner lumen with a distal opening anda proximal opening, the outer sheath sized to traverse a vasculature ofthe patient; an elongated inner sheath with a tapered distal end,wherein the tapered distal end is configured to substantially fill theinner lumen of the outer sheath and close-off the distal opening of theouter sheath, wherein the inner sheath is slidable within the innerlumen of the outer sheath, wherein the inner sheath is selectablyremovable from the inner lumen of the outer sheath by sliding the innersheath out of the proximal opening of the outer sheath; and an elongateddeployment receptacle including a deployment bay at a distal end of thedeployment receptacle and a proximal portion, wherein the deploymentreceptacle is slidable within the inner lumen of the outer sheath whenthe inner sheath is not within the inner lumen of the outer sheath,wherein the deployment bay is configured to carry the implantablemedical device through the inner lumen of the outer sheath andfacilitate deployment of the implantable medical device out of thedistal opening of the outer sheath, wherein the deployment bay includesa proximal wall that limits proximal movement of the implantable medicaldevice relative to the elongated deployment receptacle while theimplantable medical device is carried within the deployment bay, whereina transverse cross section of the proximal portion is smaller than atransverse cross section of the deployment bay.
 2. The kit of claim 1,further comprising a guidewire, wherein the inner sheath includes aguidewire lumen extending throughout the length of the inner sheath,wherein the outer sheath and the inner sheath are configured to follow aguidewire as an assembly with the guidewire lumen of the inner sheathsliding along the guidewire, wherein, in the assembly, the inner sheathis within the lumen of the outer sheath and the tapered distal end ofthe inner sheath extends beyond the distal opening of the outer sheath.3. The kit of claim 1, wherein the deployment receptacle furthercomprises a tether that is remotely controllable from a proximal end ofthe deployment receptacle to release the implantable medical device fromthe deployment bay.
 4. The kit of claim 3, wherein the tether includes ahelical element, wherein remotely controlling the tether to release theimplantable medical device from the deployment bay includes rotating thehelical element such that the helical element releases a looped elementof the implantable medical device.
 5. The kit of claim 4, whereinremotely controlling the tether to release the implantable medicaldevice from the deployment bay further includes pushing the implantablemedical device out of the deployment bay with the helical element. 6.The kit of claim 1, further comprising: a first coupling module slidablyconnected to the deployment receptacle; and a mating coupling modulesecured to a proximal end of the outer sheath, wherein the matingcoupling module is configured to connect to the first coupling modulesuch that the deployment receptacle is axially aligned with the outersheath, wherein the deployment receptacle is slidable within the outersheath while the first coupling module is connected to the matingcoupling module.
 7. The kit of claim 6, wherein the mating couplingmodule includes a valve configured to prevent bodily fluids from exitingthe patient through the inner lumen of the outer sheath, wherein thevalve is configured to open to allow the deployment receptacle to enterthe inner lumen of the outer sheath.
 8. The kit of claim 7, wherein thevalve also opens to facilitate sliding the inner sheath out of theproximal opening of the outer sheath.
 9. The kit of claim 1, furthercomprising the implantable medical device.
 10. The kit of claim 9,wherein the implantable medical device is a leadless pacemaker, whereinthe medical device includes: a housing; at least one stimulationelectrode on an exterior surface of the housing; and control circuitrywithin the housing configured to deliver cardiac stimulation therapy tothe patient via the at least stimulation electrode.
 11. The kit of claim9, wherein the medical device includes at least one sensor selected froma group consisting of: a pressure sensor; an electrocardiogram sensor; afluid flow sensor; an oxygen sensor; an accelerometer; a glucose sensor;a potassium sensor; and a thermometer.
 12. The kit of claim 9, whereinthe implantable medical device includes an expandable fixation elementdeployable from a collapsed position to an expanded position, theexpanded position configured to secure the implantable medical devicewithin a vasculature of a patient, wherein the medical device includes:a housing; at least one sensor on or within the housing; and controlcircuitry within the housing configured to monitor one or morephysiological parameters of the patient via the at least one sensor. 13.The kit of claim 12, wherein the implantable medical device isconfigured for implantation within a pulmonary artery of the patient.14. The kit of claim 9, wherein the implantable medical device includesan active fixation element configured to secure the implantable medicaldevice component to a patient tissue.
 15. The kit of claim 14, whereinthe active fixation element includes a set of active fixation tines thatare deployable from a spring-loaded position in which distal ends of theactive fixation tines point away from an implantable medical devicehousing to a hooked position in which the active fixation tines bendback towards the implantable medical device housing.
 16. A method forintravascular implantation of an implantable medical device within apatient comprising: positioning a distal end of an elongated outersheath via a vasculature of the patient proximate to a target sitewithin the patient, wherein the outer sheath forms an inner lumen with adistal opening and a proximal opening; inserting an elongated deploymentreceptacle, including a deployment bay at a distal end of the deploymentreceptacle and a proximal portion, into the proximal opening of theouter sheath, wherein the implantable medical device is positionedwithin deployment bay, wherein the deployment bay includes a proximalwall that limits proximal movement of the implantable medical devicerelative to the elongated deployment receptacle while the implantablemedical device is within the deployment bay, wherein a transverse crosssection of the proximal portion is smaller than a transverse crosssection of the deployment bay; sliding the deployment receptacle throughthe inner lumen of the outer sheath until the deployment bay is adjacentto the distal opening of the outer sheath; and deploying the implantablemedical device from the deployment bay proximate to the target sitewithin the patient.
 17. The method of claim 16, further comprising:positioning a distal end of a guidewire via the vasculature of thepatient proximate to the target site within the patient; sliding anassembly including an elongated inner sheath with a tapered distal endand the outer sheath over the guidewire to position the distal end ofthe assembly proximate to the target site within the patient, whereinthe inner sheath includes a guidewire lumen extending throughout thelength of the inner sheath, the guidewire lumen being configured toslidably receive the guidewire, wherein, in the assembly, the innersheath is within the lumen of the outer sheath and the tapered distalend of the inner sheath extends beyond the distal opening of the outersheath.
 18. The method of claim 16, wherein the deployment receptaclefurther comprises a tether that is remotely controllable from a proximalend of the deployment receptacle to release the implantable medicaldevice from the deployment bay, the method further comprising remotelycontrolling the tether to deploy the implantable medical device from thedeployment bay.
 19. The method of claim 16, wherein the target site iswithin a pulmonary artery of the patient.
 20. The method of claim 19,wherein the implantable medical device includes a pressure sensor. 21.The method of claim 16, wherein the target site is within a rightventricle of the patient.
 22. The method of claim 21, wherein theimplantable medical device is a leadless pacemaker, wherein the medicaldevice includes: a housing; at least one stimulation electrode on anexterior surface of the housing; and control circuitry within thehousing configured to deliver cardiac stimulation therapy to the patientvia the at least stimulation electrode.